– Dandruff is one of the most common hair care challenges; at least half of the adult population – including both men and women, in all ethnic groups – report having experienced it. The condition should not be confused with the normal shedding of skin cells, which is part of the regular life-cycle of all skin, including the scalp. Usually these cells are too small to be seen, although they can be noticed after shampooing, combing or brushing or scratching the scalp. read more about dandruff salon conditioners » | resource library for hair care »
In many cases, the scalp displays an increase in shedding because the skin has become dry, inflamed or infected. This can be caused by environmental factors such as extremely dry air or an allergic reaction to hair care products, particularly hair dyes or to particular ingredients in shampoos. At times, dandruff-like symptoms are caused by insufficient care of the scalp; infrequent shampooing can cause the build-up of sebum (the natural oils produced by the skin), dead skin cells and deposits of atmospheric dirt and hair care product. All of these conditions can be easily addressed with a change in the hair care regimen.
When skin shedding from the scalp becomes particularly heavy, especially when the flakes are larger and appear clumped and oily, it is a sign of a dandruff condition. The exact cause is still not clearly understood, but the mechanism seems to be a sudden increase in the skin cell turnover causing the outer layer of skin cells (called corneocytes) to be shed earlier than they should, while they are still performing a necessary function to protect the skin tissues on the scalp. In most cases, this is caused by the presence of an infection by a fungus in the Malassezia genus. This fungus metabolizes the sebum on the scalp to secrete oleic acid, which can cause the corneocytes to lose their attachment to the scalp and shed.
To complicate matters, the symptoms of dandruff can blur into another scalp condition known as seborrheic dermatitis (also called seborrheic eczema), which can occur over larger areas of the head (including in the folds of the nostrils and behind the ears) and at its most extreme can cause a layer of crusty skin to form; in infants this is sometimes called "cradle cap."
There are several treatments for dandruff, some of which address the symptoms and others which go to the causes. Shampoos and conditioners containing salicylic acid and sulphur help to break up the large flakes, so they are less visible. Coal tar also works on symptoms by reducing the rate of keratinization. Zinc pyrithione (ZPT), however, reduces the Malassezia population and diminishes the lipids (oils) on the scalp; this both decreases the infection and the conditions under which it can return. Treatments containing selenium sulfide also reduce the Malassezia infection and help relieve the seborrheic symptoms, but they can sometimes make the scalp feel oily. Other anti-fungal agents include hydroxypryiodones (marketed as Ciclopirox) and imidazole (Ketoconazole). Some shampoos also contain neem oil (derived from Azadirachta indica), which is a traditional Asian remedy for fungal infections.