Antiperspirants are cosmetics that reduce the amount of sweat. In the vast majority of products sweat reduction is achieved by using aluminium salts; primarily aluminium chlorohydrate (ACH). The astringent ACH provokes a constriction of the sweat glands. A few products contain zirconium salts or combinations of aluminium and zirconium salts.
Aluminiums salts are dissolved by the sweat, react with proteins occurring on the skin and form insoluble aluminium compounds. These substances plug the glands’ ducts with the effect to temporarily prevent sweat reaching the surface of the skin.
Antiperspirants frequently claim 24 or 48 hours protection. Authorities require that efficacy claims of cosmetic products should be substantiated scientifically i.e. Commission Regulation (EU) No 655/2013. A significant sweat reduction must be achieved for proof of efficacy of antiperspirant products. No detailed test protocol is obligatory. Antiperspirants can be tested according to the FDA “Guidelines for Effectiveness Testing of OTC Antiperspirant Drug Products” or according to different adapted procedures.
In most cases the efficacy of antiperspirants is tested by gravimetric determination. Test subjects apply the products to the axilla and are placed in special hot-rooms with defined conditions to induce sweating. Immediately after the sweating phase, the sweat is taken from the armpit using absorbent pads. The amount of sweat is determined gravimetrically.