How Chemical Hair Removal Works

Have you ever wondered how chemical hair removal (a chemical depilatory) works? Examples of common brands include Nair, Veet and Magic Shave. Chemical hair removal products are available as creams, gels, powders, aerosol and roll-ons, yet all of these forms work the same way. They essentially dissolve the hair faster than they dissolve the skin, causing the hair to fall away. The characteristic unpleasant odor associated with chemical depilatories is the smell of breaking chemical bonds between sulfur atoms in the protein.

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By Anne Marie Helmenstine, Ph.D.

The Chemistry of Chemical Hair Removal

The most common active ingredient in chemical depilatories is calcium thioglycolate, which weakens the hair by breaking the disulfide bonds in the keratin of the hair. When enough chemical bonds are broken, the hair can be rubbed or scraped off where it emerges from its follicle. The calcium thioglycolate is formed by reacting calcium hydroxide with thioglycolic acid. An excess of calcium hydroxide allows the thioglycolic acid to react with the cysteine in keratin. The chemical reaction is:

2SH-CH₂-COOH (thioglycolic acid) + R-S-S-R (cysteine) → 2R-SH + COOH-CH₂-SS-CH₂-COOH (dithiodiglycolic acid).

Keratin is found in skin as well as hair, so leaving hair removal products on the skin for an extended length of time will result in skin sensitivity and irritation. Because the chemicals only weaken the hair so that it can be scraped away from the skin, hair is only removed at the surface level. A visible shadow of subsurface hair may be seen after use and you can expect to see regrowth in 2-5 days.