The active ingredients in Nair and other chemical depilatory preparations remove hair for smooth skin that lasts longer than shaving. But of all the ingredients listed on the back of the bottle, which chemicals actually remove the hair? How do they work, and what else do they do? These are the questions a wise consumer asks before spending the money and slathering on the hair-removal cream.

Hair is made of a protein called keratin. A number of types of chemical bonds hold keratin molecules together, but it is disulfide bonds that are mainly responsible for hair's strength and durability. In Nair and other chemical depilatories, an acid and a base, or alkali, work in tandem to destroy the disulfide bonds in the hair protein.

Nair's Hair Removal Lotion for Legs formula contains calcium hydroxide, an alkali that changes the pH and texture of hair so that it is ready to react with Nair's other active ingredient, potassium thioglycolate, an acid. Potassium thioglycolate breaks the sulfide bonds in the hair keratin so that the hair can be easily wiped away. Ingredients in other depilatories will vary slightly, but they will always include an alkali and an acid that react in the presence of hair.

True to the advertised promise, Nair will provide slightly longer-lasting smooth skin than shaving. While shaved hair is cut flush with the skin and stubble can be felt within hours, hair treated with the active ingredients in Nair tends to break just below the surface of the skin, near the root. So, hair regrowth is not felt until one to three days later, depending on the individual. However, depilatory preparations do not affect the rate of hair growth, or the thickness or density of hair.

The same active ingredients in Nair that break chemical bonds in hair keratin also break down keratin in the skin. Nair promotes this as beneficial exfoliation. Chemical exfoliation is not harmful unless the product is left on the skin too long, which can cause a chemical burn. Some people with sensitive skin will experience irritation even with regular application times. For these people, sensitive skin formulations are offered by Nair and other depilatory makers.

Allergies to chemical depilatories like Nair can develop at any time, even in individuals who've used the product before with no adverse reaction, so an allergy test is recommended 24 hours before each use. Use chemical depilatories only on clean skin that is free of cuts, abrasions, sunburn or other irritation. Never exceed recommended application times.