Aluminium chlorohydrate is group of chemical compounds which have several applications. These compounds are salts, made by reacting aluminum with hydrochloric acid, and they are sometimes referred to as polyaluminium chloride, depending on the precise chemical composition and application of the compound.
In water treatment, aluminium chlorohydrate is used as a flocculant to encourage impurities in the water to clump together into flakes of material which can easily be removed. The flocculant is removed along with the flakes of impurities it generates, leaving cleaner water behind. While flocculants cannot remove all of the impurities in a given sample of water, they can help significantly with clean up, and removing bulky impurities will make additional treatments easier.
Personal care products such as deodorant and antiperspirants also contain aluminium chlorohydrate or the closely related aluminum chloride. Concentrated products designed for people who sweat heavily tend to have more of this compound to help repress and control sweating so that people will be more comfortable over the course of the day. These concentrated products are most commonly used by people with hyperhydrosis, a condition in which they sweat excessively.
Some health and safety concerns have been raised about aluminium chlorohydrate, because aluminum is capable of passing through the blood-brain barrier. Aluminum is also not nutritionally necessary, so some people have suggested that absorbing it, even in trace amounts, through the skin is probably not terribly beneficial. However, numerous studies have strongly suggested that there are no health risks to using this substance.
Claims that these compounds cause cancer have not been substantiated, despite extensive research by several organizations, and no link between aluminium chlorohydrate and Alzheimer's disease or other neurological problems have been discovered, despite the fact that it can pass through the blood-brain barrier. Given this information, these compounds are generally recognized as safe, although people may not necessarily want to consume them or use them excessively.
For people who prefer to err on the side of caution, deodorant and antiperspirant products which are free of aluminium chlorohydrate and other aluminum compounds are available, although they can be slightly more expensive. The effectiveness of such products varies considerably as well; one reason aluminium chlorohydrate is used in some many products is that it is highly effective. Those concerned about odor in particular could consider taking other measures, such as discarding old garments which house odor-causing bacteria, or making dietary changes to produce less pungent sweat.