Antiperspirants have been widely used since the mid 1960s. In 1978, the US Food and Drug Administration (FDA) issued a draft monograph (finalized in 1993) on the category, listing these products as drugs—defined as an over-the-counter (OTC) drug when applied topically to reduce production of underarm sweat (perspiration).1 Antiperspirants and deodorants are considered drugs because they can affect the function of the body by reducing the amount of sweat that reaches the skin surface. In the United States, OTC drugs are subjected to monograph rules, which define standards and requirements, pre-market approval process, acceptable actives and allowable formulation percentages of actives. Other countries’ regulations vary in content and scope. Even though most countries have not adopted equal FDA regulatory restrictions, they have adopted some type of general regulatory guidelines that define acceptable safe antiperspirant actives and how to substantiate claims. Even though non-US antiperspirant products are not confined to strict rules, because the FDA monograph has become a template of acceptable antiperspirants, there has been limited innovation in the category globally.
The consumer typically confuses the function of antiperspirants and deodorants, mostly due to a misunderstanding of marketing claims and product positioning. For the most part, antiperspirants are built upon aluminum-based cationic salt chloride complexes, as well as complexes with zirconium acid salts, and are referred to as “actives” on the label. There are numerous types of antiperspirant actives listed in the FDA monograph as well as in the United States Pharmacopeia (USP).2 Antiperspirant actives are responsible for blocking sweat expulsion through the formation of temporary plugs within the sweat duct, thus stopping or slowing down the flow of sweat to the surface of the eccrine gland. The mechanism of sweat reduction is not based on a physiological change to the body. The mechanism is typically described as an occlusive protein-precipitation plug with the acidic nature of the antiperspirant to produce an aluminum or zirconium hydroxide plug. This plug is superficial and readily reversible after 7–28 days without use. The formulation matrix delivery system is the key to effectiveness and acceptable consumer antiperspirant systems. The most common delivery systems are roll-ons (either aqueous or cyclosiloxane suspensions), aerosol (hydrocarbon propellant suspensions), extrudable clear gels (water-in-cyclosiloxane emulsions), extrudable opaque soft solids (anhydrous cyclosiloxane suspension pastes) or solid sticks (anhydrous cyclomethicone suspension solids), as shown in Figure 1.