Why Do Antiperspirants Fail?

      Unwanted armpit sweat remains a common problem. Clearly, the biggest advance in sweat reduction is the injection of botulinum toxin, also known as Botox. Yet, antiperspirants remain an excellent solution. Antiperspirants can even be combined with Botox to prolong or increase the effect. Optimizing your antiperspirant involves understanding how they function and why they fail.

      What is an antiperspirant?

      Antiperspirants are classified as over-the-counter (OTC) drugs and must follow certain safety guidelines. The most important guideline is that the ingredient that decreases sweat must be selected from an approved list and used in concentrations no greater than specified.

      Antiperspirants are intended to reduce the amount of sweat that is released by the eccrine sweat glands and ducts onto the skin surface. They are distinct from deodorants, which are intended simply to make the skin smell better. Most antiperspirants function as deodorants by decreasing the substrate available for bacterial growth, however deodorants do not function as antiperspirants.

      What is sweat?

      Sweat can be divided into apocrine and eccrine perspiration. Eccrine sweat is a clear, odorless fluid of pH 4-6.8 composed of 98-99% water, sodium chloride, lower fatty acids, lactic acid, citric acid, ascorbic acid, urea, and uric acid. Apocrine sweat is a turbid, viscous, odorless fluid of pH 6-7.5 that has high content water, in addition to protein, carbohydrate waste materials, and sodium chloride. The amount of eccrine perspiration is much greater than the amount of apocrine perspiration. An effective antiperspirant must reduce both types of perspiration.

      How does an antiperspirant reduce sweat?

      The reduction of sweat is a daunting task. In the axilla, there are some 25,000 sweat glands capable of producing large quantities of perspiration in response to heat and emotional stimuli. Antiperspirants work by coagulating the protein the sweat duct. They contain metal salts that combine with skin protein to cause sweat duct closure that obstructs sweat flow to the skin surface.

      The only two metal salts that are presently used in antiperspirants are aluminum and zirconium. The original antiperspirant formulation was a 25% solution of aluminum chloride hexahydrate in distilled water, but it was extremely irritating. More modern antiperspirant formulations contain aluminum chloride, aluminum chlorohydrate, aluminum zirconium chlorohydrate, and buffered aluminum sulfate. These metals provide a better balance between efficacy and skin irritation.

      How are antiperspirants evaluated?

      An antiperspirant must reduce sweat by at least 20% to be marketed in the US. Antiperspirants that are labeled as highly effective must reduce sweat by at least 30%. Efficacy is defined as the percentage reduction in the rate of sweating achieved after application of the antiperspirant product. The percentage sweating reduction can be determined gravimetrically. This involves weighing an absorbent pad and then placing the pad in the armpit while the subject is induced to sweat in a hot room. The pad is then reweighed after a specified time in the hot room and the increase in weigh per time is converted into a sweating rate. The rate can be compared before and after the application of an antiperspirant.

      How can antiperspirants work better?

      An effective antiperspirant must create a long lasting plug in the sweat duct quickly. This is best accomplished by evenly spreading the antiperspirant in the armpit. If the antiperspirant does not touch the sweat duct, it will not work. The ability to evenly distribute the antiperspirant accounts for the decreased efficacy of aerosol spray formulations that may easily miss sweat gland containing areas.

      The most effective antiperspirants are the sticks and lotions. These are vigorously rubbed in the armpit to remove the product from the specially designed applicator to distribute the chemical throughout the armpit. The active agent in the newer antiperspirants is aluminum-zirconium tetrachlorohydrex-gly complex. This complex can reduce armpit sweat by 40-60%.

      Why do antiperspirants fail?

      Understanding why antiperspirants fail is indeed complex. Probably the most common reason for antiperspirant failure is that the formulation does not contain an optimal active ingredient mix and appropriate vehicle construction to deliver the best results. For this reason, people with sweating problems should not select unbranded antiperspirants sold at a lower price point. Better antiperspirant formulations contain costlier ingredients and will not be the cheapest on the shelf.

      The next most common reason for antiperspirant failure is the inability to get an even film that covers the entire armpit. The antiperspirant must be in contact with each and every sweat duct in the armpit to work. Thus, the applicator should be domed to fit into the armpit and dispense a thick even film of product. The film must be somewhat water resistant or it will be rinsed away by perspiration. For this reason, the armpit should be dry when the product is applied.

      Another possible cause for antiperspirant failure is inconsistent application. Compliance is important to achieve optimal results. It takes about 10 days of antiperspirant application for the complete plug to be formed in the sweat duct. If you decide after 3 days of application that the antiperspirant has not worked sufficiently, you have not given the product an adequate trial. Furthermore, the plug is completely gone 14 days after the last application. Continuous daily application is necessary to achieve and maintain the sweat reduction effect.

      Another consideration is the depth of the plug within the sweat duct. Plugs that are more deeply placed in the sweat gland will provide better sweat reduction than those that are at the skin surface. If the plug is very close to the surface, it is possible that it can be removed by the rubbing of clothing or shaving. People who complain that antiperspirants do not work may wish to wear loose fitting clothing around the armpits and use only light razor pressure when shaving the armpits. The deepest plugs are created by prescription aluminum chloride solutions, but these formulations must be used carefully as they can irritate skin and ruin natural fabrics, such as rayon, cotton, and silk. More superficial plugs are created by OTC antiperspirants containing aluminum chlorohydrate. Intermediate depth plugs are created by OTC antiperspirants containing aluminum zirconium chlorohydrate.

      What can be done to optimize topical antiperspirant efficacy?

      Optimizing antiperspirant efficacy requires the use of a well-formulated product that is consistently applied to the entire armpit as a thin film. Efficacy can be further enhanced by applying the antiperspirant twice daily. The bedtime application is actually more important than the morning application because the body is at rest and sweating reduced. The reduced sweating decreases the removal of the antiperspirant from the armpit and allows the active ingredient to remain in contact with the skin longer creating a stronger plug.