Aluminium salts are the active ingredient in antiperspirants, reducing wetness and odour from underarm sweating. Deodorants are different from antiperspirants; they contain fragrances to mask perspiration odour, but do not prevent perspiration or the associated odour.

Some inaccurate rumours have suggested that the aluminium in antiperspirants is a cause of breast cancer. However, a large number of studies show that antiperspirants do not cause cancer, or pose any health risks, either through the use of aluminium or the reduction of sweating.

The skin does not  absorb aluminium very well, and antiperspirants do not penetrate into the skin or the sweat glands.

Antiperspirants form a thin layer on the skin, over the sweat ducts where they are applied. They do not block perspiration from sweat ducts in the rest of the body.

Sweat is not a major route of eliminating toxins from the body; antiperspirants do not prevent the release of toxins from the body in sweat, or force toxins back into the body.

Almost all of the toxins and other waste products of the body are filtered out by the kidneys and liver and are then excreted. The function of sweat glands is to control body temperature and sweat consists mostly of water.

Many reliable studies have been done on the safety of aluminium in antiperspirants and other personal care products. The overwhelming conclusion is that antiperspirants that contain aluminium do not cause breast cancer or other illnesses; a few key studies are noted below, and additional sources of information are listed in the following section.

The American Cancer Society states that scientific evidence does not link breast cancer risk with antiperspirant use. It notes that “a carefully designed epidemiologic study of this issue found no link between breast cancer risk and antiperspirant use, deodorant use, or underarm shaving.”

In 2008, another major French review of 59 published scientific studies on antiperspirants found no evidence of a link between antiperspirants and breast cancer.