well as prevention of sweating within the sockets of prosthetic devices used by amputees. Acidifiers and pH neutral products – deodorants that prevent bacterial action by enhancing (or at least, not depleting) the skin's natural slight acidity, known as the acid mantle, which naturally reduces bacterial action but can be compromised by typically alkaline soaps and skin products. Masking scents – other strong or overriding scents of a pleasing type may be used, used to mask bodily odors. Typically these are strongly smelling plant extracts or synthetic aromas. Activated charcoal and other products capable of absorbing sweat and/or smell. Although charcoal most often has a black color, the activated charcoal used in deodorants may be a very light color for aesthetic reasons. Less commonly used, products such as milk of magnesia (a thick liquid suspension of magnesium hydroxide) are sometimes used as deodorants. Many milk of magnesia products contain small amounts of sodium hypochlorite (bleach) at very low levels that are safe for ingestion and skin application. Sodium hypochlorite is a powerful bactericide, and it is possible that its presence in a product that can dry onto the skin, may explain this use as a deodorant. (Safety info: bleach is caustic and extremely poisonous, and can be lethal, in higher concentrations.) Formats 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 North America, solid or gel forms are dominant. Health effects 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. Unscented deodorant is available for those with sensitive skin. Frequent use of deodorants was associated with blood concentrations of the synthetic musk galaxolide. Aluminum Many deodorants and antiperspirants contain aluminium in the form of aluminium salts such as aluminium chlorohydrate. The US Food and Drug Administration, in a 2003 paper discussing deodorant safety, concluded 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 aluminum containing antiperspirants", therefore allowing their use and