What is the perfect method for cleansing the face? This is a question I get asked daily in my practice. The truth is, I am not sure how to best wash the face. There are many acceptable methods of removing sebum and environmental dirt from the face, but the single best method is probably somewhat controversial. I casually asked 30 dermatologists for their patient facial cleansing recommendations and received about 7-10 different and equally credible answers. I shall endeavor in this article to provide an overview of some of the new facial cleansing techniques currently on the market.
Many dermatologists related to me that they tell their patients never to use soap on their face. I suspect they are referring to soap in the chemical sense as a reaction between a fat and an alkali resulting in a fatty acid salt with detergent properties. There are currently three different types of bar cleansers on the market all called "soap." There are the true soaps, which are composed of long chain fatty acid alkali salts with a pH between 9-10. These are probably the "soap" products that the dermatologists were in favor of avoiding. The high pH of these cleansers is excellent at thoroughly removing sebum, but can also damage the intercellular lipids in diseased or sensitive skin. The next type of "soap" products are known as synthetic detergents, or syndets, and contain less than 10% real "soap" with a pH adjusted to 5.5-7. These are the cleansers that form the bulk of the products found in a dermatologist's sample closet and are less likely to damage the intercellular lipids, but also may not remove all of the sebum from extremely oily skin. A third type of "soap," known as a combar, combines alkaline soaps with syndets to create a bar with greater cleansing abilities, but less intercellular lipid damage.
Selecting the proper type of "soap" may be tricky for the dermatologist, but once the three categories of cleansers are identified the task becomes much easier. In general, all beauty bars, mild cleansing bars, and sensitive skin bars are of the syndet variety (Oil of Olay, Dove, Cetaphil). Most deodorant bars or highly fragranced bars are of the combar variety (Dial, Coast, Irish Spring) and very few true soaps are currently on the market (Ivory).
Lipid-free cleansers are liquid products that clean without fats, which distinguishes them from the soap type cleansers previously discussed. They are applied to dry or moistened skin, rubbed to produce a lather, and rinsed or wiped away (Cetaphil cleanser, Aquanil). These products may contain water, glycerin, cetyl alcohol, stearyl alcohol, sodium laurel sulfate and occasionally propylene glycol. They leave behind a thin moisturizing film and can be used effectively in persons with excessively dry, sensitive, or dermatitic skin. They do not have strong antibacterial properties, however, and may not remove odor from the armpit or groin. They also are not good at removing excessive environmental dirt or sebum. Lipid-free cleansers are best used where minimal cleansing is desired.
Cleansing creams are popular among mature women who grew up in an era where cleansing cream offered the only alternative to the harsh alkaline soaps of the past previously discussed. Cleansing creams are composed of water, mineral oil, petrolatum, and waxes. The most common variant of cleansing cream, known as cold cream, is created by adding borax to mineral oil and beeswax (Pond's Cold Cream). These products are popular to remove cosmetics and provide cleansing for patients with dry skin in one step.
The recognition that exfoliation of desquamating corneocytes was desirable to produce smooth skin in maturing patients, led to the concept of an abrasive scrub. Abrasive scrubs incorporate polyethylene beads, aluminum oxide, ground fruit pits, or sodium tetraborate decahydrate granules to induce various degrees of exfoliation. The most abrasive scrub is produced by aluminum oxide particles and ground fruit pits. In general, products containing these rough edged particulates are not appropriate for sensitive skin patients. More mild facial scrubbing is produced by polyethylene beads which are smooth and round (Clinique 7th Day Scrub). The least aggressive abrasion of the skin is found in products that contain sodium tetraborate decahydrate granules, which soften and dissolve during use. The main problem with abrasive scrub products for epidermabrasion is the firm nature of the scrubbing granules that do not deform when pressed too hard against the skin.
Woven mesh products were introduced about the same time as abrasive scrubs to also induce exfoliation, but with an implement instead of a particulate. The most popular product to enter the marketplace was composed of a nonwoven polyester fiber web sponge (Buf Puf). Originally, this product was designed to remove open comedones, but later the web stiffness was decreased and the sponge impregnated with a mild cleanser to produce products designed for various skin types.
The desire for thorough, but less abrasive cleansing led to the development of the disposable cleansing cloth. These cloths are composed of a combination of polyester, rayon, cotton, and cellulose fibers held together via heat through a technique known as thermobonding. Additional strength is imparted to the wipe by hydroentangling the fibers. This is achieved by entwining the individual rayon, polyester, and wood pulp fibers with high pressure jets of water, which eliminates the need for adhesive binders thereby creating a soft, strong cloth. These clothes are packaged dry and impregnated with a cleanser that foams modestly when the cloth is moistened. The type of cleanser in the cloth depends whether strong sebum removal is required by oily skin or modest sebum removal is required by dry skin. Humectants and emollients can also be added to the cloth to decrease barrier damage with cleansing or to smooth the skin scale present in xerosis.
In addition to the composition of the ingredients preapplied to the dry cloth, the weave of the cloth will also determine its cutaneous effect. There are two types of fiber weaves used in facial products: open weave and closed weave. Open weave cloths are so named because of the 2-3 mm windows in the cloth between the adjacent fiber bundles. These clothes are used in persons with dry and/or sensitive skin to increase the softness of the cloth and decrease the surface area contact between the cloth and the skin yielding a milder exfoliant effect. Closed weave cloths, on the hand, are designed with a much tighter weave and provide a more aggressive exfoliation. Ultimately, the degree of exfoliation achieved is dependent on the cloth weave, the pressure with which the cloth is stroked over the skin surface, and the length of time the cloth is applied.
The cleansing pouch represents a variation on the fibered cloths, however it can also be used as a metered delivery system for skin cleansing and conditioning agents. It is possible to place a plastic membrane between two fibered cloths containing holes of various diameters. The size of the hole determines how quickly the contents of the pouch are released onto the skin surface. Typically, the cleansing pouch does not produce as much exfoliation as a plain cleansing cloth.
The newest mechanized technique for facial cleansing is the face brush (Clarisonic, Pacific Biosciences Laboratories). This device was developed by the same team of engineers and researchers that developed the Sonicare Toothbrush (Phillips). The hand-held device runs on a rechargeable battery that is attached to a miniaturized motor creating an oscillatory motion of the brush head. This oscillatory sonic motion was developed to more thoroughly remove plaque from the teeth. A revision of the enlarged brush head with softer tufted bristles was developed for facial cleansing.
I had the opportunity to informally study this brush to determine the degree of facial cleansing provided as part of a funded research grant from Pacific Biosciences Laboratories, Seattle, WA. We elected to apply a dark facial foundation and powder to the faces of Caucasian women and then attempt to remove the makeup with various cleansers. We cleansed the face using a timed cleansing sequence with a lipid-free cleanser, foaming face wash, abrasive polyethylene bead scrub, face cloth, and the face brush. After completion of the cleansing sequence, we took an isopropyl alcohol soaked sponge and swabbed the face vigorously to remove any remaining cosmetic. The amount of dark foundation left behind after the cleansing technique provided a nice contract on the white rubber sponge. We found that the least amount of cosmetic was removed with the lipid-free cleanser followed by foaming syndet-based face wash. These products cleansed the skin surface, but did not clean as well in the dermatoglyphics. This effect was more pronounced in individuals with prominent pores and/or acne scarring. The abrasive polyethylene bead scrub removed more facial foundation, but not as much as the face cloth. This is probably due to the more even traversal of the skin surface with the textured face cloth amongst the dermatoglyphics. However, the face brush produced the most thorough facial foundation removal. The face brush bristles were able to traverse the dermatoglyphics, facial pores, and facial scars more adeptly than any other cleansing method.
The better facial foundation removal with the face brush may be due to the ability of the closely spaced tufted flexible bristles to reach all of the uneven surfaces of the facial skin. The sonic motion of the brush also aided in dislodging the facial foundation particles, much like the sonic surgical instrument cleansers that are used to dislodge debris in liposuction cannulas and reusable injection needles.
We also had the opportunity to use the brush in a variety of individuals with various dermatologic conditions to include acne, trichostasis spinulosa, pseudofollicultitis barbae, and seborrheic dermatitis. While the face brush provided excellent cleansing of the uneven skin surface in all these conditions, the most impressive results were seen in seborrheic dermatitis. The face brush was able to adeptly remove the skin scale in the facial folds, as well as in the hairy areas of the face, such as the eyebrows. Adequate cleansing of eyebrows and the male beard has always been a challenge due to the dense coarse nature of the hair. The sonic motion of the brush, as opposed to the more common rotary facial brushes, allows the face brush to traverse hair-bearing skin without tangling the hair in the brush. The brush was also good for cleaning in and behind the ears. While more research is needed to verify these early results, it may be that this technology originally developed for dental use may have some dermatologic utility, as well.
This article has examined various cleansing methods using a variety of cleansers, implements, and mechanized devices. Each method offers unique advantages to the user.
The skin is an extremely versatile organ for the delivery of active agents. Substances that affect the physiology of the skin can be administered parenterally or topically. Topical application can be achieved through rubbing a variety of vehicles on the skin to include gels, lotions, solutions, creams, ointments, etc. Typically these products are wiped from a jar, squeezed from a tube, sprayed from a can, or poured from a bottled and rubbed by the hands onto the affected area. Yet, there is another effective method of applying skin products based on the application of the active substance to a fibered cloth, which is then stroked across the skin.
Fibered cloths have been entering the recent skin care consumer marketplace with great rapidity as a novel method of delivering various benefits to the skin. These clothes can be premoistened and impregnated with surfactants to cleanse the diaper area, they can be perfumed containing volatile solvents to freshen the hands, they can be packaged dry with lipids and soaps to clean the face, they can cover a plastic film pouch with microscopic holes to time release an active onto the skin surface, etc. There can be no doubt that fibered paper products need to be studied as a dermatologic delivery system. This article will attempt to elucidate the value of their profound effect.
The first fibered clothes were introduced 30 years ago as baby wipes. They were made from carded rayon fibers that were held together by adhesive binders. They exhibited wonderful strength for their thickness, but were rather coarse and a frequent cause of irritant contact dermatitis due to both the surfactants employed and the rough cloth texture. The need for a strong, but soft cloth led to development of air-laid nonwoven fibered clothes in the mid 1970s. These clothes were composed of wood pulp, polyester, and adhesive binders. These clothes were thicker and softer. The technology was further developed in the 1980s by adding both cotton and rayon fibers to improve strength.
Modern fibered cloth technology has focused on creating a soft wipe with excellent strength to prevent tearing. The fibers used are a combination of polyester, rayon, cotton, and cellulose fibers, but they are held together via heat through a technique known as thermobonding. Additional strength is imparted to the wipe by hydroentangling the fibers. This is achieved by entwining the individual rayon, polyester, and wood pulp fibers with high pressure jets of water. Thermobonding and hydroentangling have eliminated the use of adhesive binders thereby creating a soft, strong cloth. These newly created fibered cloths are soft enough for use on the face, eyelids, and wounded skin.
In addition to advances in cloth technology, there have also been advances in cleansing technology. Diaper wipes were originally wetted with water and ethanol or isopropanol. These ingredients caused stratum corneum barrier damage and rapidly evaporated from the opened, unused wipes. Modern diaper wipes contain an oil-in-water emulsion in the form of a lotion composed of preservatives, surfactants, emollients, humectants, fragrances, and skin protectants. The skin protectant used in many wipes is allantoin, an ingredient listed in the FDA Diaper Rash Protectant Monograph. Recently, diaper wipe technology has been adapted to adult use as a form of moist toilet paper.
Last year saw the introduction of the facial cleansing cloth. These clothes use the same fabric as diaper wipes, but a different weave designed to address the unique needs of the face. Face clothes are packaged dry and impregnated with a cleanser that foams modestly when the cloth is moistened. The type of cleanser in the cloth depends whether strong sebum removal is required by oily skin or modest sebum removal is required by dry skin. Humectants and emollients can also be added to the cloth to decrease barrier damage with cleansing or to smooth the skin scale present in xerosis. With these techniques, face cloths can be designed for normal to oily skin, normal to dry skin, or sensitive skin.
In addition to the composition of the ingredients preapplied to the dry cloth, the weave of the cloth will also determine its cutaneous effect. There are two types of fiber weaves used in facial products: open weave and closed weave. Open weave cloths are so named because of the 2-3 mm windows in the cloth between the adjacent fiber bundles. These clothes are used in persons with dry and/or sensitive skin to increase the softness of the cloth and decrease the surface area contact between the cloth and the skin yielding a milder exfoliant effect. Closed weave cloths, on the hand, are designed with a much tighter weave and are double sided. One side of the closed weave cloth is textured and impregnated with a synthetic detergent cleanser designed to optimize the removal of sebum, cosmetics, and environmental dirt while providing an exfoliant effect. The opposite side of the cloth is smooth and designed for rinsing the face and possibly applying skin conditioning agents.
The texture of the cloth provides a mechanical exfoliation that may be valuable in the patient who cannot tolerate chemical exfoliation through the use of hydroxy acids. The mechanical exfoliation can be achieved on the skin surface and the follicular ostia due to the ability of the textured cloth to traverse the irregular topography of the skin more effectively than the hands or a wash cloth. The degree of exfoliation achieved is dependent on the cloth weave, the pressure with which the cloth is stroked over the skin surface, and the length of time the cloth is applied.
Adapting wipe technology to sunscreen application has been an active area of research. One of the main shortcomings of sunscreen is the inability of the user to apply the product in an even film. Typically, the sunscreen is inadequately applied to skin that falls between the fingers of the rubbing hand. Multiple coats and circular application motion can decrease the chances of creating skin areas devoid of sunscreen, yet application of sunscreen with a fibered cloth offers the possibility of more even deposition of a continuous thickness film over the body. Sunscreen actives appropriate for application in this manner include zinc oxide, titanium dioxide, and octylmethoxycinnamate, among others. The sunscreen wipe also offers an easy to carry disposable package that is less messy. Perhaps the application ease would encourage sunscreen application compliance among both adults and children.
The primary advantage of the fibered cloth as an applicator over the hand is uniformity of film formation. It is difficult to apply product evenly with the fingertips to a skin surface, since the fingertips have a limited application surface area. A wipe, on the other hand, creates a uniform surface from which the product can be applied to the skin. Future uses for wipe technology include the application of skin care products and topical medications.
Fibered clothes can also be used as a metered delivery system. It is possible to place a plastic membrane within two layers of fibered cloth with minute holes of various diameters. The size of the hole would be the rate-limiting step in delivery of the active to the skin surface. For example, an area of lichen simplex chronicus could be treated by placing a topical corticosteroid in the pouch and attaching it to the skin for sustained continuous metered delivery. A hydroquinone-containing pouch could be attached to an area of resistant dyspigmentation overnight to treat a darkened skin area refractory to previous treatment. Similar technology could also be used to delivery wound healing agents to chronic leg ulcers. Expensive immune modulators could be applied to treatment resistant psoriatic plaques to minimize product cost by preventing the waste of expensive actives. One pouch could be applied to the skin over several nightly treatment sessions with a color shift indicator signaling when the pouch has been depleted of active.
Hand sanitizers represent a new category of skin care product with both benefits and challenges for dermatology. It is amazing to think that hand sanitizers were listed by USA Today in 2007 as one of the 25 inventions that changed modern life during the past 25 years along with cell phones. Hand sanitizers are found in hotel lobbies, school cafeterias, purses, glove compartments, and on key chains. It is standard practice for physicians to use hand sanitizers between examining patients in hospitals and even visitors to hospitals are required to use hand sanitizer in the lobby before entering the facility. Hand sanitizers are considered over-the-counter drugs and are regulated by the FDA. What exactly is the composition of hand sanitizers? How do they work? Do they decrease the spread of disease? What are the limitations of hand sanitizers? Why do hand sanitizers contribute to hand dermatitis? These are the questions that this article will explore.
Hand sanitizers fall in several categories based on composition: alcohols, quaternary ammonium compounds, and triclosan. Each of these active ingredients possesses different antimicrobial properties and acts through a different mechanism. It is worthwhile to explore the different categories to better understand product efficacy.
The largest category of hand sanitizers is based on alcohols. Alcohols has been used for disinfection for over 100 years and are highly effective because they nonspecifically denature proteins. The most effective alcohol used in hand sanitizers is ethanol, which is generally recognized as safe and effective by the FDA. Substances that meet this criteria are known as GRASE ingredients. Ethanol has excellent killing against both gram positive and gram negative bacteria and fungal organisms. However, ethanol is not effective against bacterial spores and has variable efficacy in killing enveloped viruses.
Another category of hand sanitizers is based on quaternary ammonium compounds, such as benzaklonium chloride or benzethonium chloride. While the ethanol-based hand sanitizers are flammable, the quaternary ammonium compounds are not and can be used in special circumstances. Quaternary ammonium compounds adsorb to the cytoplasmic membrane of microbes causing leakage of cytoplasmic contents. They are bacteriostatic against gram positive bacteria and some gram negative bacteria and fungistatic. They are not active against nonenveloped viruses. It is interesting to note that some species of Staphylococcus aureus carry a gene that allows resistance to quaternary ammounium compounds. These organisms are also more likely to be antibiotic resistant, as well. Quarternary ammonium compound hand sanitizers may not be the best choice where methicillin resistant Staphylococcus aureus (MRSA) is a concern.
Triclosan is a commonly used antibacterial in a wide variety of products including deodorant soaps, toothpastes, and mouth washes. It is chemically known as 2,4,4’-trichloro-2’-hydroxydiphenyl ether. It is a chlorinated phenolic compound that is also used as a surgical scrub. Triclosan kills organisms by damaging the cell membrane, but has weak activity against gram negative bacteria, such as Pseudomonas. Recent FDA concerns have been expressed regarding the widespread use of triclosan and its environmental impact accompanies by concerns of possible growing bacterial resistance.
There is no doubt that the Center for Disease Control (CDC) considers hand sanitizers to be a mainstay in the prevention of worldwide disease transmission. Alcohol-based hand sanitizers have become an international standard for hand hygiene as endorsed by the World Health Organization (WHO) as part of its Patient Safety Initiative. They promote hand hygiene compliance as they do not require water and dry quickly on the hands. They can be used under a variety of circumstances by adults and children and do not require a visit to a restroom. The biggest transmission of disease occurs from hand-to-hand contact between persons and hand-to-mouth or hand-to-nose or hand-to-eye contact within an individual. Hand hygiene is key to disease prevention and hand sanitizers have been credited with reducing the impact of several worldwide influenza and other infectious epidemics.
While hand sanitizers have played an important part in limiting the spread of contagious disease, they also possess some important limitations. They do not kill all organisms. For example, hand sanitizers are not effective against anthrax, which was of great concern several years ago. Hand sanitizers are also not effective against Clostridium difficile, which has become another antibiotic resistant organism. Hand sanitizers are not good at removing visible dirt from the hands and are best used on clean hands that might contain nonvisible dirt.
Hand sanitizers are a new cause of recalcitrant hand dermatitis. However, a study in health care workers demonstrated better skin condition with the use of hand sanitizers as opposed to frequent hand washing. The popular ethanol based hand sanitizers are quite effective at solubulizing components of the intercellular lipids. Eventually, the skin barrier is compromised with repeated use and dermatitis ensues. As the dermatitis causes fissures that lead to bleeding, many patients may be even more aggressive in their hand sanitizer use as they are concerned about infection and the spread of blood to others. This further worsens the hand dermatitis leading to a cycle of increasing problems. It is difficult for barrier restoration to occur amid frequent ethanol application.
One solution to the problem is to minimize or eliminate hand sanitizer use, unless absolutely necessary. This should be accompanied by the use of topical corticosteroids to reduce inflammation applied twice daily, recognizing that most of the barrier repair will occur at night when the hands are inactive. At night, on top of the topical corticosteroid, a glycerin-based occlusive hand cream should be applied. The hand cream is very important to creating an environment for barrier repair. Healing usually occurs in 2 weeks, at which time the topical corticosteroid can be discontinued, but the hand cream application should continue at bed time indefinitely. Night time repair is the key to off setting the damaging effects of hand sanitizer during the day.
Hand sanitizers have become an important part of hand hygiene both for physicians and consumers. The spread of infectious disease by the hands of physicians from patient to patient can be minimized along with the spread of disease in the general population. Ethanol-based hand sanitizers seem to dominate the marketplace because of their quick drying time, low cost, and high efficacy. Unfortunately, ethanol is a strong solvent and can rapidly damage the intercellular lipids. Daytime use of hand sanitizers must be balanced with nighttime use of a glycerin-based occlusive hand cream to restore hand skin barrier function.
In 2001, consumers spent approximately $100 million on OTC acne treatment products. Some OTC anti-acne products are cosmetics. These products do not have an active ingredient listed on the packaging. Once acne products list an active ingredient, the US Food and Drug Administration (FDA) classifies them as OTC drugs. Only certain ingredients can be used in acne products, which are listed in the Acne Monograph. These ingredients are aimed at reducing the number of acne blemishes, acne pimples, blackheads and whiteheads. Ingredients approved for this use on the monograph include: salicylic acid, sulfur, sulfur combined with resorcinol, and benzoyl peroxide. These ingredients can only be used singly and not in combination. Other botanical extracts that are not on the monograph are also used, such as hydroxy acids, retinol, triclosan, and tea tree oil. The utility of these ingredients in the treatment of acne is discussed.
The most effective and most commonly used active ingredient in OTC acne preparations is benzoyl peroxide. 23% of persons age 13 to 27 years have used an OTC benzoyl peroxide product. It is member of the organic peroxide family consisting of two benzoyl groups joined by a peroxide group. Benzoyl peroxide is prepared by reacting sodium peroxide with benzoyl chloride to yield benzoyl peroxide and sodium chloride. It is a radical initiator and highly flammable, explosive, a possible tumor promoter, and mutagen.
Benzoyl peroxide was not originally developed for medical purposes. It first appeared in 1917 as an ingredient to bleach flour white. It was first used medically to treat leg ulcers in the 1960s and then for the treatment of acne in the 1970s. Other applications include its use for tooth whitening and as an active agent in hair dyes.
Benzoyl peroxide has many properties pertinent to acne, including antibacterial, anti-inflammatory and comedolytic effects. When benzoyl peroxide touches the skin, it breaks down into benzoic acid and oxygen, neither of which is problematic. It has antimicrobial properties against P. acnes as demonstrated by a 2-log10 decrease in P. acnes concentration after two days of 5% benzoyl peroxide topical application. This same antimicrobial effect was also observed with 10% benzoyl peroxide resulting a mean 2-log10 decrease in organisms after applying 10% benzoyl peroxide cream for three days, however, after seven days, no further decline in P. acnes level was observed.
These are interesting studies because they point to several interesting facts about topical benzoyl peroxide. The first finding is that 5% and 10% benzoyl peroxide may be equally efficacious, meaning that the increased skin irritation experienced with the higher concentration may not be necessary to improve acne resolution. Furthermore, initial improvement in acne may be seen with topical benzoyl peroxide as P. acnes killing is occurring, but eventually no further decline in organisms is possible. The patient may notice a decrease in acne lesions for a short period, but acne that is due other factors will not improve. This accounts for the common patient perceived phenomenon where the product worked well initially, but eventually “resistance” occurred and no further improvement was noted. This is why many consumers change from OTC acne product to OTC acne product to OTC acne product as each successive treatment “looses potency.” There is no loss in potency. It is simply that the benzoyl peroxide has done what is possible and further improvement requires the addition of another ingredient from either the OTC or the prescription realm.
Benzoyl peroxide in an important antimicrobial, with better P. acnes killing than any other topical antibiotic alone, such as erythromycin or clindamycin. However, unlike topical antibiotics, benzoyl peroxide does not result in resistant organisms. This is the rationale for the currently popular combination of benzoyl peroxide and clindamycin in cream or gel prescription formulations. Even a benzoyl peroxide cleanser can suppress the development of resistant organisms. Thus, benzoyl peroxide is ubiquitous found in many acne treatment regimens.
Benzoyl peroxide also acts as an anti-inflammatory agent by reducing oxygen radicals. Further, its ability to reduce the P. acnes population also reduces inflammation due to lessened bacterial induced monocytes producing tumor necrosis factor-alpha, interleukin-1beta, and interleukin-8. This anti-inflammatory effect is perceived by the patient as reduced redness and pain.
Finally, benzoyl peroxide is also a comedolytic, capable of producing a 10% reduction in comedones. Comedolytics allow the plug in the pore to loosen from the surrounding follicle restoring the normal flow of sebum to the skin surface. It was originally thought that higher concentration benzoyl peroxide preparations provided superior comedolytic benefits, however it now appears that even 2.5% benzoyl peroxide is effective. Higher concentration benzoyl peroxides may only increase skin irritation, resulting in peeling and redness. In addition, benzoyl peroxide is a cause of allergic contact dermatitis in 1-2.5% of consumers, resulting in redness, swelling, oozing, and pain. Benzoyl peroxide can also bleach clothing and hair.
One of the major unresolved concerns regarding benzoyl peroxide is its safety. Benzoyl peroxide is a highly reactive molecule capable of causing explosions in concentrations of 20% or higher. The manufacture of benzoyl peroxide products requires a special facility and stability problems are common in new formulations. Benzoyl peroxide is capable of producing DNA strand breaks, but rodent carcinogenicity studies have been negative. No correlation has been shown between benzoyl peroxide use and skin cancer in humans.
Current trends in benzoyl peroxide formulation have focused on the use of less irritating hydrogel formulations and smaller particle size benzoyl peroxide. Raw benzoyl peroxide is a particulate that must be solubulized into solution. It is only the benzoyl peroxide that touches the skin surface that is active in the killing of P. acnes. Larger particles yield higher concentrations in the formulation, but most of the benzoyl peroxide does not touch the skin. Smaller particle size allows better skin coverage with less irritation, since the concentration is reduced. It is possible to create a 2.5% benzoyl peroxide formulation with equal efficacy to a 10% benzoyl peroxide formulation based on skin contact with the active. Careful, creative formulation can minimize tolerability issues with OTC benzoyl peroxide formulations.
The other major comedolytic used as an active in OTC acne treatments is salicylic acid in concentrations up to 2%. Salicylic acid is a colorless crystalline oil soluble phenolic compound originally derived from the willow tree Salix. It is a beta hydroxy acid where the OH group is adjacent to the carboxyl group. Synthesis of the compound involves the treating of sodium phenolate, the sodium salt of phenol, with carbon dioxide at 100atm pressure and 390K temperature followed by acidification with sulfuric acid.
Salicylic acid, also known as 2-hydroxybenzoic acid, has a rich history in medicine. It is used as an anti-inflammatory inhibiting arachidonic acid, since it is chemically related to aspirin, a flavoring agent with the characteristic wintergreen taste, a liniment for sore muscles, and an acne treatment. Hippocrates in the 5th century BC wrote about a bitter powder extracted from the willow back that would ease pain and reduce fever. The active extract of the willow back, called salicin, was isolated in crystalline form by Henri Leroux, a French pharmacist, in 1828.
Salicylic acid can penetrate into the follicle and dislodge the comedonal plug from the follicular lining. It does not kill P. acnes, however, and does not prevent the development of antibiotic resistance. Thus, salicylic acid maybe less effective than benzoyl peroxide in acne treatment, but it is also less irritating and less allergenic. Some proprietary salicylic acid preparations have shown parity to 5% benzoyl peroxide. Salicylic acid is sometimes used in hypoallergenic acne treatments and acne treatments for mature individuals.
Salicylic acid can be applied to the skin in a variety of different formulations. It can be applied as a solution in an alcohol-detergent vehicle or in the form of an impregnated pad., It can be formulated as a 2% salicylic acid scrub with clinical data demonstrating a reduction in open comedones. 10% and 20% salicylic peels are also used to promote comedolysis.
Some individuals experience allergic reactions when salicylic acid is ingested, however, it is generally accepted as a safe ingredient. An overdose of salicylic acid can lead to salicylate intoxication, presenting as a state of metabolic acidosis with a compensatory respiratory alkalosis. This has not been reported with topical applications and salicylic acid acne preparations are considered safe and effective, even during pregnancy.
The oldest treatment for acne predating benzoyl peroxide and salicylic acid is sulfur. Sulfur is a known bacteriostatic and antifungal. It is a yellow, nonmetallic element that has been used for centuries to treat various dermatologic conditions. A Roman physician first described the use of a sulfur mineral bath for the treatment of acne in an early medical text named HYPERLINK "http://en.wikipedia.org/wiki/De_Medicina" De Medicina . The mechanism of action for sulfur is not totally understood, but it is thought to interact with cysteine in the stratum corneum causing a reduction in sulfur to hydrogen sulfide. Hydrogen sulfide in turn degrades keratin producing the keratolytic effect of sulfur. Sulfur has been labeled as a comedogen, but this is controversial.
Sulfur is available in concentrations of 3-8% in OTC acne formulations. It has a characteristic foul odor and unusual yellow color. It stains clothing and is typically formulated as a thick paste. This limits its utility, however it commonly used in prescription formulations in combination with sodium sulfacetamide, a topical sulfa antibiotic.
In addition to the monographed acne treatment ingredients of salicylic acid, sulfur, and benzoyl peroxide, other substances have been used to improve the appearance of acne-afflicted skin. These substances include: hydroxy acids, retinol, triclosan, and tea tree oil.
Hydroxy acids, such as glycolic acid, have also been used in acne treatments as desquamating agents. Glycolic acid is the smallest alpha hydroxy acid appearing as a colorless, odorless, hygroscopic crystalline solid. While glycolic acid can be obtained from the fermentation of sugar cane, it is more commonly synthesized by reacting chloroacetic acid with sodium hydroxide followed by re-acidification.
The efficacy of glycolic acid in treating acne is related to the free acid concentration. The free acid is able to dissolve the ionic bonds between the corneocytes forming the stratum corneum. This desquamation can remove the comedonal plugs, however the water-soluble glycolic acid cannot enter the oily milieu of the pore. For this reason, salicylic acid is a much better comedolytic.
Glycolic acid can be delivered to the skin in the form of a cleanser, moisturizer, or peel. The rinse-off cleanser is less effective in acne therapy than the leave-on moisturizer. Higher 20-70% glycolic acid can be delivered to the skin in the form of a peel that is left on for 3-5 minutes followed by rinsing. The peels can also be used to improve the dark scarring associated with acne, known as post-inflammatory hyperpigmentation.
Topical antimicrobials may also be used in the treatment of acne. One common antimicrobial used in deodorant soaps and waterless hand sanitizers is triclosan. Triclosan is not on the US Acne Monograph, but is used for the treatment of acne in other countries, such as the England. Triclosan decreases P. acnes counts on the skin surface, which accounts for the dermatologist recommendation that acne patients use deodorant soap as part of an acne treatment regimen. Other delivery methods for triclosan, including hydrogel patch delivery, have been published.
Vitamin A derivatives, known as retinoids, are used in the treatment of acne both in the prescription and the OTC realm. Three prescription acne treatment retinoids exist: adapalene, tretinoin, and tazarotene. Unfortunately, prescription retinoids have the unwanted side effect of dryness, peeling, and irritation of the skin.
A variety of OTC retinoids exist that may be helpful in acne. These retinoids include retinol and retinaldehyde. Retinol can be absorbed by keratinocytes and reversibly oxidized into retinaldehyde. Retinaldehyde is irreversibly converted into all-trans retinoic acid, known as tretinoin, a potent prescription retinoid. Tretinoin is transported into the keratinocyte nucleus modulating cellular behavior and normalizing follicular keratinization.
There are no large multicenter trials that evaluate the efficacy of OTC retinoids. In general, the retinols are twenty times less potent than topical tretinoin but exhibit greater penetration than tretinoin. 0.25% topical retinol induces cellular and molecular changes similar to that observed with 0.025% tretinoin without causing the irritation typical of tretinoin.
Tea tree oil is the most common herbal essential oil used for acne treatment. Tea tree oil, obtained from the Australian tree Melaleuca alternifolia, contains several antimicrobial substances including: terpinen-4-ol, alpha-terpineol and alpha-pinene. It appears as a pale golden oil with a fresh camphoraceous odor. It is used for medicinal purposes as an antiseptic, antifungal, and antibacterial.
The antibacterial activity of 10% tea tree oil has been shown against staphylococcus aureus, including methicillin resistant staphylococcus aureus (MRSA), without resistance. Lower concentrations, however, have demonstrated bacterial resistance. Tea tree oil has been found to be as effective in the treatment of acne as 5% benzoyl peroxide based on a reduction in comedones and inflammatory acne lesions, however the onset of action was slower for tea tree oil. The tea oil group did experience fewer side effects than the benzoyl peroxide group. Another randomized 60 subject placebo-controlled study in subjects with mild to moderate found 5% topical tea tree oil produced a statistically significant reduction in total lesion count and acne severity index as compared to placebo. Tea tree oil may also reduce the amount of inflammation present around acne lesions thereby reducing redness.
Tea tree oil is toxic when swallowed. It also has produced toxicity when applied topically in high concentrations to cats and other animals. It use in low concentration topically for the treatment of acne has not produced toxicity problems. However, tea tree oil is a known cause of allergic contact dermatitis. An Italian study of 725 subjects patch tested with undiluted, 1%, and 0.1% tea tree oil found that 6% of subjects experienced a positive reaction to undiluted tea tree oil, 1 subject experience an allergic reaction to 1% tea tree oil, and no subjects experienced a reaction to the 0.1% dilution. Thus, the incidence of allergic reactions to tea tree oil is concentration dependent.
Dermatology encompasses diseases of the vermillion border, lips, and oral mucosa. Dermatologists are consulted for many diseases of the mouth including lichen planus, mucous cysts, irritant and allergic contact dermatitis, xerostomia, and geographic tongue. For this reason, it might be worthwhile to initiate a discussion of toothpaste, which is as important to oral hygiene, as soap is to skin hygiene. The technologic developments in toothpaste formulation have been great over the past few years. This article examines those aspects of toothpaste that are important to the dermatologist who is asked to evaluate oral conditions.
The oral cavity is a complex structure consisting of the gums, tongue, and mucosa that is bathed in saliva composed of water and enzymes. Intervening are the teeth and accompanying nerve endings along with bacteria and mold with the effects of the breath moving across them. All of this is complicated by the addition of food and drink creating an environment where many different factors interact on a minute-to-minute basis. Toothpaste is charged with the task of keeping all of these tissues healthy while meeting aesthetic and taste challenges. Since all of the toothpaste is never completely rinsed from the mouth, it must also be harmless if ingested.
Toothpaste must be formulated at a pH close to that of the saliva, which is between 6.6-6.9. Toothpaste pH is usually slightly higher than that of saliva to buffer the effect of acidic drinks and also to inhibit the bacterial fermentation of food residue. The paste must be water soluble to mix with saliva usually containing substances such as glycerol, sorbitol, and xylitol to function as humectants allow the paste to mix and hold water while brushed across the teeth. Abrasives are included to scrap plaque from the teeth along with thickeners.
One of the goals of toothpaste is to polish the enamel of the teeth. In time, tooth surfaces are coated by a thick layer of protein that must be removed to prevent bacterial growth. The abrasive must not damage the underlying harder enamel. Problems can arise when gum recession occurs exposing the dentine due to aging or poor tooth brushing habits. The dentin is softer than the enamel and can be damaged from the abrasives. The abrasives currently used are precipitated silica gels, aluminum oxide, or baking soda. The abrasives accompanied by the act of brushing serve to clean the teeth.
Toothpaste also produces sensations within the mouth to compliment the cleaning produced by the abrasives and brushing. These include flavoring agents and substances to create the residual feeling of freshness. Many toothpastes contain sweeteners, such as sodium saccharin. Menthol is frequently used to leave the mouth with a cool, clean feel and to mask breath odor between brushings. Mint and spearmint are the most commonly used flavors.
The toothpaste must also be thickened and contain an agent to produce foaming. Polymers are used to thicken toothpaste including sodium carboxy-methyl cellulose or hydroxyl-ethyl cellulose and xanthan or guar gums. The thickener must easily dissolve in the mouth with saliva so the paste does not become lumpy. Traditional detergents are used for foaming, such as sodium lauryl sulfate (SLS) at 1-1.5% concentrations.
The appearance of the toothpaste is also part of the cleansing experience. Most toothpastes are actually translucent with the addition of 1% micronized titanium dioxide, the same substance used in inorganic sunscreens, to make them opaque. Some toothpastes are pigmented to create positive consumer perceptions. For example, pink is felt to represent healthy gums and green to represent a minty fresh taste. Sometimes these colors are mixed to create an aesthetically pleasing striped effect for branding purposes.
The breakdown of tooth enamel is the precipitating factor leading to dental caries. Enamel strengthening is one of the largest categories of toothpaste that may have accounted for the worldwide improvement in dental health. The main ingredients in enamel strengthening are sodium fluoride, stannous fluoride, and sodium mono-fluoro-phosphate. Teeth are made up of calcium hydroxyapatite with ions, such as hydroxyl and carbonate fluorides that are in equilibrium between the tooth and the saliva. Brushing with a fluoride ion containing solution can increase the amount of fluoride ions present in the tooth apatite lattice. As the fluoride is deposited in the tooth, it creates a stronger crystalline lattice and makes the tooth more acid resistant. For this reason, stannous fluoride has been found to decrease dental caries. Most enamel strengthening toothpastes contain between 0.1-0.15% fluoride ions with a few prescription products containing up to 0.5%.
Gingivitis or inflammation of the gums is an important health issue that can improve oral health. Gingivitis is due to bacteria present in the mouth, which give rise to tartar and plaque formation, providing the need for antibacterial toothpaste formulations. The most commonly used antibacterial is triclosan, also found in deodorant soaps and some hand sanitizers. Chlorhexidine gluconate is also used, but high concentrations can cause teeth browning. There is concern that triclosan could disturb the resident bacteria in the mouth, but triclosan is highly effective in reducing bad breath and mouth odor.
Another popular consumer need is tooth whitening. This was popularized initially in the dentist’s office, but now has spread to products in the mass market. Tooth whitening toothpastes are used to maintain professional tooth whitening or to whiten teeth discolored by coffee, tea, or smoking. The most common tooth whitening substance is hydrogen peroxide, which releases oxygen in the mouth oxidizing the protein film on the tooth making it appear more luminous. The oxygen can also decrease bacterial tooth colonization.
Tartar, also known as calculus, is a hard plaque present on the tooth surface formed by saliva, debris, and insoluble minerals. Bacteria can live on the plaque releasing acidic substances that degrade tooth enamel leading to dental caries. Tartar control toothpastes contain pyrophosphates to prevent tartar formation.
Another important need, especially with an aging population, is the desensitization of teeth due to the expose of tooth roots with gum recession. Tooth roots are covered with a soft protective material known as cementum, which is easily softened by acids and can be removed by abrasives. Acids are present in foods, especially soft drinks, sport drinks, and fruit juices. These acids can also cause dental erosion now being seen in children. Sipping on acidic drinks, such as from a bottle or a covered cup with a spout, is especially problematic. Wine, salad dressings, and vinegar are also highly acidic foods that are damaging to the teeth until rinsed thoroughly with saliva. Once the cementum is removed, pathways connecting the tooth to the nerve are open allowing for sensitivity.
Dentine is composed of microscopic tubules 0.5-2mm in diameter. One way to decrease tooth sensitivity is to plug the porosity of these tubules. This can be accomplished with calcium-base chemistry that allows natural tooth minerals to deposit back into the tubules. There are several methods of accomplishing this goal. Strontium chloride was the active agent in the first commercially successful sensitive toothpaste (Sensodyne, GlaxoSmithKline). In this toothpaste, the strontium chloride precipitated from the toothpaste along with phosphate and calcium from the saliva in the dentin tubules. With continued use, more precipitation occurs eventually plugging the tubules and preventing pain.
A newer approach to sealing dentine tubules and reducing tooth sensitivity is the use of nanoparticle hydroxyappatite. The nanoparticle hydroxyappatite is intended to increase the transport of calcium back into the dentin tubules and reduce sensitivity (Apagard, Sangi).
In 1999, the Center for Disease Control published that fluorination of public water supplies was one of the 10 most important health accomplishments of the 20th century. The fluorination of metropolitan water supplies in the US has led to decreased dental decay, but many individuals still use well water in smaller more remote areas of the US. Fluroination is also not practiced around the world making toothpaste an important source of fluoride. Stannous fluoride is the most effect fluoride formulation and can deposit a protective barrier into dentine tubules and exposed tooth surfaces decreasing decay and reducing tooth sensitivity. The development of stannous fluoride toothpastes may account for the increase in mature individuals who still retain their own teeth.
This article has examined toothpaste formulation and its role in optimizing oral hygiene while preventing dental decay. Toothpaste is as important to oral hygiene as cleansing is to good skin hygiene.