People with dandruff may experience embarrassment because it is felt that dandruff is caused by a fungus. The cause of dandruff is still unknown, but a yeast-like fungus, malassezia globosa, which is specific to the scalp, has been labelled as the...
Malassezia lives on the scalp of most healthy adults without creating any problems. In adults who do not have dandruff, the scalp continually replaces itself by shedding mature skin cells about once per month. It is normal for skin cells to die and flake off. Dry skin sometimes causes flaking but the flakes are usually smaller and less oily than those flakes caused by dandruff.
Stress and fatigue
Whatever causes malassezia to overgrow causes dandruff. Increased oil production, hormonal changes, stress and fatigue are usually implicated. People who have poor immune systems, those who have Parkinson's disease and others who are recovering from heart attack and stroke have shown some susceptibility to developing dandruff.
Other contributing factors include infrequent shampooing of the hair and scalp; using hair products which contain alcohol, and using styling gels, sprays and waxes which can cause oily build up on the hair and scalp.
Frequent washing (daily if possible) with a gentle shampoo usually removes the flakes and reduces oil and dead-cell build up. Persistent dandruff may be treated with medicated shampoos. These shampoos should be left on the hair, scalp or affected skin for at least five minutes before rinsing to allow the active ingredients to work.
Shampoos containing selenium sulphide (Selsun Blue) prevent the rapid cell turnover of dandruff and reduce the malassezia fungus. The shampoo may discolour gray hair. It may also discolour chemically coloured or processed hair, so it should not be used within 48 hours of colouring or straightening hair.
Zinc pyrithione is an active ingredient of some anti-dandruff shampoos (Head and Shoulders, Selsun, Keracare). It is an anti-fungal which reduces the malassezia fungus.
Coal tar-based shampoos (Neutrogena T-Gel, Polytar) and salicylic acid preparations (Acneflex, Tinasol) reduce the overproduction of new skin cells and break down the dandruffy scales which are then washed off while shampooing.
Salicylic acid preparations may leave the scalp extra dry, leading to more flaking and so using a conditioner afterwards is advisable.
Ketoconazole is a powerful anti-fungal available in two shampoo strengths - the over-the-counter strength (Triatop) and the prescription-only strength (Nizoral).
If dandruff persists despite using one shampoo faithfully for several weeks, alternating with another type of dandruff shampoo may produce better results. Otherwise, a medical doctor or dermatologist may decide whether you should be prescribed steroid treatment to relieve the itchy rash caused by skin inflammation or prescription-strength ketoconazole (Nizoral) shampoo.
Dahlia McDaniel is a pharmacist and final year doctoral candidate in public health at the University of London; email: firstname.lastname@example.org.