Human sweat itself is largely odorless until it is fermented by bacteria that thrive in hot, humid environments such as the human underarm. The armpits are among the consistently warmest areas on the surface of the human body, and sweat glands provide moisture. Underarm hair adds to the odor by providing increased surface area on which this bacteria thrive. Body odor is controlled by reducing moisture, killing bacteria or over powering the bacteria's smell with perfume.<unk> s — classified and regulated as over-the-counter (OTC) cosmetics by the U.S. Food and Drug Administration (FDA)[citation needed] — work to inhibit the growth of bacteria which cause odors. The first commercial<unk> , Mum, was introduced in the late nineteenth century.<unk> s are usually alcohol-based, which kills bacteria effectively.<unk> s can be formulated with other, more persistent antimicrobials such as triclosan, or with metal chelant compounds that slow bacterial growth.<unk> s also often contain perfume fragrances intended to mask the odor of perspiration.<unk> s may be combined with antiperspirants — classified as drugs by the FDA — which attempt to stop or significantly reduce perspiration and thus reduce the moist climate in which bacteria thrive.  Aluminum chloride, aluminum chlorohydrate, and aluminum-zirconium compounds, most notably Aluminum zirconium tetrachlorohydrex gly and Aluminum zirconium trichlorohydrex gly, are the most widely used antiperspirants. Aluminum-based complexes react with the electrolytes in the sweat to form a gel plug in the duct of the sweat gland. The plugs prevent the gland from excreting liquid and are removed over time by the natural sloughing of the skin. The blockage of a large number of sweat glands reduces the amount of sweat produced in the underarms, though this may vary from person to person.
A popular alternative to modern commercial<unk> s is Ammonium alum, which is a common type of Alum sold in crystal form. It has been used as a<unk>  throughout history in Thailand, the Far East, Mexico and other countries.<unk> s and antiperspirants come in many forms. What is commonly used varies in different countries. In Europe, aerosol sprays are popular, as are cream and roll-on forms which are prevalent in less affluent parts of the world. In the United States, solid or gel forms are dominant.
Deodorant
Herbicide
Detergent
Food additive
Antimetabolite
Inhalant
Analgesic
Antimicrobial