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Many individuals apply either deodorant or antiperspirant before heading out. Some products combine both roles, aiming to manage sweat and underarm odor. Our underarms contain two types of glands: apocrine and eccrine. The eccrine glands, which are far more abundant, produce the majority of sweat in our underarms and across our bodies.
While some use deodorants to mask underarm odors, those who sweat excessively often require antiperspirants to reduce sweat production. Our bodies continuously generate sweat, but certain triggers like heat, physical activity, stress, or anxiety can increase its production. When stimulated, sweat glands release a fluid that travels through ducts to the skin's surface.
Solid antiperspirants contain various components, such as wax, liquid emollients, and active-ingredient compounds. The active ingredient is what enables antiperspirants to block sweat. All antiperspirants rely on an aluminum-based compound as their primary ingredient, which is always listed first on the product label. Below are some common active ingredients:
- Aluminum chloride
- Aluminum zirconium tricholorohydrex glycine
- Aluminum chlorohydrate
- Aluminum hydroxybromide
According to dermatologist Dr. Eric Hanson from the University of North Carolina's Department of Dermatology, aluminum ions are absorbed by the cells lining the eccrine-gland ducts at the epidermis (the skin's outermost layer). As these ions enter the cells, water follows, causing the cells to expand and compress the ducts, effectively blocking sweat from escaping.
Cells can only absorb a limited amount of water, so once the water concentration inside and outside the cells balances, osmosis causes the water to exit the cells, reducing their swelling. This explains why antiperspirant reapplication is necessary. For individuals with hyperhydrosis (excessive sweating), high concentrations of aluminum chloride can extend the swelling period and may even shrink the sweat glands, reducing their sweat production.
Typical over-the-counter antiperspirants contain active-ingredient concentrations ranging from 10 to 25 percent. The FDA mandates that these products must not exceed 15 to 25 percent active ingredient, depending on the type, and must reduce sweat production by at least 20 percent for the average person. For severe underarm sweating, prescription antiperspirants with higher concentrations are available.
