Dandruff can be best described as excessive shedding of dead cells from the scalp. Shedding of dead cells is normal as long as it is not excessive. It is part of the normal process of cell renewal. The cells form in lower skin levels and are gradually pushed upwards by the new, growing cells that form underneath. By the time the cells reach the skin surface, they have died and become flat and they overlap each other like roof tiles and are ready to depart the scalp. In a normal, healthy scalp, the dead cells leave the surface unnoticeably. With dandruff, the whole process is accelerated and a larger number of dead cells are shed, forming big clumps that are visible to the naked eye. Dandruff is very common and some estimates say that it affects up to 50% of the population at some point in their lives.
There are three main causes and types of dandruff and each one of them has to be treated differently. Many people mistake dandruff for dry scalp and start shampooing their hair less frequently, which, in the case of dandruff, leads to a worsening of their condition. The most common cause of dandruff is the overgrowth of a fungus that normally lives in our scalp and is called malassezia. This fungus feeds on the natural grease in the scalp, converting it into oleic acid. The reasons for the sudden proliferation of this fungus are not exactly known.
Seborrhoeic dermatitis leads to a more severe form of dandruff than malassezia, causing greasy bran-like scale. Seborrhoeic dermatitis is usually accompanied by skin inflammation that, besides the scalp, also affects the eyebrows, the skin around your nose, ears and the lines on your cheeks, forehead and armpits. In moderate climates this condition typically improves in summer as direct sunlight relieves its symptoms. Cradle cap, however frightening it may look, is a mild form of seborrhoeic dermatitis affecting only infants and it clears itself by the time the baby turns one year old.
Psoriasis is the third known cause of dandruff, leading to its most serious form. It causes itchiness and inflammation of the skin and produces thick, silvery scales which occur most often in the scalp, knees and lower back. Psoriasis results in rapid shedding of the dead skin and, if this shedding occurs from the scalp, it is known as dandruff. This condition affects about 2% of the population and like the two aforementioned forms of dandruff, it is not contagious. An excessively oily scalp, hormonal imbalances, autoimmune disorders, elevated scalp sensitivity, heart problems, extreme stress, etc. are often associated with an increased occurrence of all forms of dandruff. It has also been observed that some cases of dandruff are triggered by chemicals contained in hair care products. However, the exact cause of any of the aforementioned dandruff-triggering conditions is not known.
When it comes to available treatment options, for a start it sometimes helps to wash your hair more often and use a mild shampoo. In more severe conditions it is advisable to try some of the special anti-dandruff shampoos freely available in pharmacies. For yet more severe cases you will need to see your doctor to prescribe you a prescription strength shampoo, which typically contains the same active ingredients as OTC products but in a higher concentration. The active substances used in anti-dandruff shampoos can include any of the following: salicylic acid, coal tar, zinc pyrithione, sulphur, selenium sulphide, ketoconazole, corticosteroids and caffeine. Each one of them addresses the problem from a different angle. For the most serious conditions, corticosteroid and anthralin treatments will typically be prescribed by your doctor.