Dandruff is the shedding of the scalp’s epidermal cells, something that affects most people in various degrees. The skin of the scalp constantly sheds, but when the scalp’s dead cells shed at a rapid rate, large grey-white clumps appear on the top of the scalp and become visible. Manufacturers of shampoos and conditioners have produced an array of safe and unsafe over-the-counter products that have been sold under both the banner of beauty and medicine to eliminate or prevent dandruff.
Mild forms of dandruff are the most common and are easily treated by washing the hair more frequently, but more serious conditions also produce similar kinds of itching and flakes. Seborrheic dermatitis, for example, is often difficult to distinguish from dandruff, but it is treated with a prescription drug. People with oily scalps more easily produce yeast and thus tend to suffer most from seborrheic dermatitis, dandruff, and Pityrosporum ovale, which leads to scalp irritation and scaling. The yeast is rare among children, but its prevalence tends to increase with age. Males are also more likely than females to experience dandruff, probably because of the yet-unclear effect of androgen hormones. More severe dandruff may also indicate a fungal infection or another dermatological disorder such as psoriasis, a skin disease that must be treated by a dermatologist and that can occur on other parts of the body than the scalp.
For individuals who do not find relief from shampooing, drug products may help. Mild dandruff is typically treated with popular over-the-counter shampoos such as Selsun Blue or the aptly named Head and Shoulders. In 1990, the U.S. Food and Drug Administration (FDA) banned 27 unsafe or ineffective ingredients commonly found in dandruff shampoos. There are currently five ingredients that the FDA has determined to be safe and effective, including coal tar, pyrithione zinc, sulfur, selenium sulfide, and salicylic acid. However, not all problems with these ingredients have been eliminated. Coal tar not only leaves an orange tint that often lingers after the shampoo has been used, especially in light-colored or dyed hair, but one form of treated bituminous coal increases sensitivity to sunlight, and long-term use is associated with skin cancer. Products that include coal tar advise its use only for a short-term basis.