How do anti-perspirant deodorants work?

Sweat itself has no odour as it is mostly water, cooling the body as it evaporates from the skin. The problem arises when perspiration from the apocrine glands -- located primarily in the underarm and genital regions -- is broken down by bacteria on the skin surface.

The desire to control sweat and odour is not new. As far back as the first century B.C., humans used aromatic oils to try to mask body odour. Over the years, modern science has given us more technologically advanced means of controlling wetness and odour. Deodorants and anti-perspirants are the most popular of these modern "remedies." Each performs a unique role -- deodorants help prevent odour while anti-perspirants help prevent odour and reduce wetness.

Deodorants
Deodorants help prevent underarm odour in three ways:

	Bactericides (bacteria-killing agents) such as alcohol or propylene glycol kill odour-causing bacteria already present in the underarm area.
	A bacteriostat (bacteria-retardant) such as triclosan or benzethonium chloride helps to prevent future bacterial growth.
	A pleasant fragrance masks any residual odour.

Anti-Perspirants
Anti-perspirants help prevent underarm odour in the same way that deodorants do, but also reduce the flow of perspiration to the surface of the skin.

The active ingredients in anti-perspirant products (usually aluminium salts) mix with perspiration inside the sweat ducts. The difference in pH between the salts and the perspiration forms a "precipitate," which then acts as a harmless and temporary plug to prevent perspiration from reaching the skin's surface.

In North America, anti-perspirants are regulated as Category I OTC (over the counter) products, which means they are considered safe and effective. The FDA requires that a product reduce sweat by a minimum of 20% in order to be labelled an anti-perspirant.