Hair lightening is a popular cosmetic process that can be performed at a salon or at home. It is used either to simply lighten the overall tint of the hair or to prepare it for coloring with a dye. The main active ingredient in most hair bleaches is hydrogen peroxide. Additional active ingredients generally include some combination of ammonium or potassium persulfate and alcohol (isopropyl, ethyl or cetearyl).
Proper use of hair bleach is one of the main factors that determine the safety level of the bleaching process. Pretesting is necessary to rule out the likelihood of an allergic reaction. Bleach must be kept away from the eyes and should not make any prolonged contact with the skin (highlighting mixtures should not touch the scalp at all). Appropriate ventilation helps prevent the buildup of chemical fumes during processing. Wearing protective gloves and not leaving the lightener on for too long are also standard precautions.
Many individuals are allergic to one or more of the active ingredients in hair bleach. Allergic reactions can manifest as hives (painful, itchy welts). These may occur the first time a particular bleaching product is used or during any subsequent use. Ammonium persulfate in particular is known to trigger asthma attacks and other respiratory symptoms in allergy-prone individuals. Improper use can cause chemical burns and blisters on the skin. Bleach is a highly poisonous substance that should never be ingested.
The bleaching process works by oxidizing melanin and other components in the hair. This chemical reaction is somewhat harmful to hair since oxidation is the same process as burning--just at a lower heat and a slower rate. Leaving the mixture in place for too long or bleaching the hair repeatedly can cause serious damage to the cuticle. Bleached hair often becomes fragile and may fall out at a faster than normal rate. Even proper application leaves hair in need of frequent conditioning to avoid breakage.
The Food and Drug Administration has limited control over the ingredients used in hair products since they are generally considered to be cosmetics rather than drugs. Just because a particular brand of hair bleach has no caution or warning labels does not mean the FDA considers it to be safe or that it contains only approved chemicals. Individuals with allergies or sensitive skin should always review the entire list of ingredients on the back of the package before using any hair-lightening product.
A popular alternative to chemical bleaches is the application of lemon juice followed by exposure to UV radiation from the sun. This can highlight the hair but won't turn a brunette into a blond. It still dries the hair out to some extent. In March of 2009, Japanese scientist Dr. Kenzo Koike announced at the national meeting of the American Chemical Society that an eco-friendly hair bleach is under development. It uses fungal enzymes activated by a small amount of hydrogen peroxide to lighten hair. This new product may eventually provide a safer option for users who wish to avoid the harsh, damaging effects of current hair-bleaching products.