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A deodorant is a substance applied to the body to prevent body odour caused by the bacterial breakdown of perspiration in armpits, feet, and other areas of the body. A subgroup of deodorants, antiperspirants, affect odour as well as prevent sweating by affecting sweat glands.
Antiperspirants are typically applied to the underarms, while deodorants may also be used on feet and other areas in the form of body sprays. Aerosol antiperspirant products may, however, be applied to non-underarm body areas where excessive sweating (hyperhidrosis) is a problem. Aerosol antiperspirants may be particularly helpful to control sweat on the feet. It's recommended that a person try the antiperspirant on a small area of the skin first, to make sure that he/she does not have a reaction to it. Solid-form antiperspirants may be used along the hairline or bra line if these areas have problematic sweating. Again, test on a small area of the skin first. In the United States, the Food and Drug Administration classifies and regulates most deodorants as cosmetics, but classifies antiperspirants as over-the-counter drugs.
The first commercial deodorant, Mum, was introduced and patented in the late nineteenth century by an inventor in Philadelphia, Pennsylvania, whose name has been lost to history. The product was briefly withdrawn from the market in the U.S., but is currently available at U.S. retailers under the brand Ban. The modern formulation of the antiperspirant was patented by Jules Montenier on January 28, 1941. This formulation was first found in "Stopette" deodorant spray, which Time Magazine called "the best-selling deodorant of the early 1950s". Stopette was later eclipsed by many other brands as the 1941 patent expired.
A small percentage of people are allergic to aluminium and may experience contact dermatitis when exposed to deodorants containing aluminium. There is a popular myth that deodorant use is linked to breast cancer, but research has shown no such link exists.
Human perspiration is largely odourless until it is fermented by bacteria that thrive in hot, humid environments. The human underarm is among the most consistently warm areas on the surface of the human body, and sweat glands provide moisture, which when excreted, has a vital cooling effect. When adult armpits are washed with alkaline pH soap, the skin loses its acid mantle (pH 4.5 - 6), raising the skin pH and disrupting the skin barrier. As many bacteria thrive in this elevated pH environment, this makes the skin susceptible to bacterial colonization. The bacteria feed on the sweat from the apocrine glands and on dead skin and hair cells, releasing trans-3-Methyl-2-hexenoic acid in their waste, which is the primary cause of body odour. Underarm hair wicks the moisture away from the skin and aids in keeping the skin dry enough to prevent or diminish bacterial colonization. The hair is less susceptible to bacterial growth and therefore is ideal for preventing the bacterial odour.
Deodorants are classified and regulated as cosmetics by the U.S. Food and Drug Administration (FDA) and are designed to eliminate odour. Deodorants are usually alcohol-based. Alcohol initially stimulates sweating, but may also temporarily kill bacteria. Deodorants can be formulated with other, more persistent antimicrobials such as triclosan, or with metal chelant compounds that slow bacterial growth. Deodorants may contain perfume fragrances or natural essential oils intended to mask the odour of perspiration.
Deodorants combined with antiperspirant agents are classified as drugs by the FDA. Antiperspirants attempt to stop or significantly reduce perspiration and thus reduce the moist climate in which bacteria thrive. Aluminium chloride, aluminium chlorohydrate, and aluminium-zirconium compounds, most notably aluminium zirconium tetrachlorohydrex gly and aluminium zirconium trichlorohydrex gly, are frequently used in antiperspirants. Aluminium chlorohydrate and aluminium zirconium tetrachlorohydrate gly are the most frequent active ingredients in commercial antiperspirants. Aluminium-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 metal salts work in another way to prevent sweat from reaching the surface of the skin: the aluminium salts interact with the keratin fibrils in the sweat ducts and form a physical plug that prevents sweat from reaching the skin’s surface. Aluminium salts also have a slight astringent effect on the pores; causing them to contract, further preventing sweat from reaching the surface 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.
Over-the-counter products labelled as "natural deodorant crystal" containing the chemical potassium alum have gained new-found popularity as an alternative health product, in spite of concerns about their contact dermatitis. A popular alternative to modern commercial deodorants is ammonium alum, which is a common type of alum sold in crystal form and often referred to as a deodorant crystal. It has been used as a deodorant throughout history in Thailand, the Far East, Mexico and other countries.
Deodorants 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. In the United States, solid or gel forms are dominant.
In the 9th century, Ziryab introduced under-arm deodorants in Al-Andalus from Baghdad. In 1888, the first commercial deodorant, Mum, was developed and patented by a U.S. inventor in Philadelphia, Pennsylvania, whose name has been lost to history. The small company was bought by Bristol-Myers in 1931 and in the late 1940s, marketing executive Edward Gelsthorpe decided to develop an applicator based on the newly invented ball-point pen. In 1952, the company began marketing the product under the name Ban Roll-On. The product was briefly withdrawn from the market in the U.S. It is once again available at retailers in the U.S. under the brand Ban. In the UK it is sold under the names Mum Solid and Mum Pump Spray. Chattem acquired Ban deodorant brand in 1998 and subsequently sold it to Kao Corporation in 2000.
In 1903, the first commercial antiperspirant was Everdry. The modern formulation of the antiperspirant was patented by Jules Montenier on January 28, 1941. This patent addressed the problem of the excessive acidity of aluminium chloride and its excessive irritation of the skin, by combining it with a soluble nitrile or a similar compound. This formulation was first found in "Stopette" deodorant spray, which Time Magazine called "the best-selling deodorant of the early 1950s". "Stopette" gained its prominence as the first and long-time sponsor of the game show What's My Line?, and was later eclipsed by many other brands as the 1941 patent expired.
In the early 1960s, the first aerosol antiperspirant in the marketplace was Gillette's Right Guard, whose brand was later sold to Henkel in 2006. Aerosols were popular because they let the user dispense a spray without coming in contact with the underarm area. By the late 1960s, half of all the antiperspirants sold in the U.S. were aerosols, and continued to grow in all sales to 82% by the early 1970s. However, in the late 1970s two problems arose which greatly changed the popularity of these products. First, in 1977 the Food and Drug Administration (FDA) banned the active ingredient used in aerosols, aluminium zirconium chemicals, due to safety concerns over long term inhalation. Second, the Environmental Protection Agency (EPA) limited the use of chlorofluorocarbon (CFC) propellants used in aerosols due to awareness that these gases can contribute to depleting the ozone layer. As the popularity of aerosols slowly decreased, stick antiperspirants became more and more popular. Today, sticks are the most popular type of antiperspirant.
The health impact of deodorant use is disputed. A small percentage of people are allergic to aluminium and may experience contact dermatitis when exposed to aluminium-containing deodorants. After using a deodorant containing zirconium, the skin may develop an allergic, axillary granuloma response. Antiperspirants with propylene glycol, when applied to the axillae, can cause irritation and may promote sensitization to other ingredients in the antiperspirant. Deodorant crystals containing synthetically made potassium alum were found to be a weak irritant to the skin. Alcohol-free deodorant is available for those with sensitive skin. Frequent use of deodorants was associated with blood concentrations of the synthetic musk galaxolide.
A preliminary study (2001) showed that the use of aluminium chlorohydrate, the active ingredient in many antiperspirants, does not lead to a significant (vs. ingestion via diet) increase in aluminium levels in the body with one-time use. The Food and Drug Administration, in a monograph dedicated to analysing the safety of deodorants, concluding that "Despite many investigators looking at this issue, the agency does not find data from topical and inhalation chronic exposure animal and human studies submitted to date sufficient to change the monograph status of aluminium containing antiperspirants", therefore allowing their use and vowing to keep monitoring the scientific literature.
Aerosol burns and frostbite
If aerosol deodorant is held close to the skin for long enough, it can cause an aerosol burn—a form of frostbite. In controlled tests, spray deodorants have been shown to cause temperature drops of over 60 °C in a short period of time.
Aluminium zirconium tetrachlorohydrex gly, a common antiperspirant, can react with sweat to create yellow stains on clothing. Underarm liners are an alternative to antiperspirants that do not leave stains.
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