Dandruff is a common skin condition that affects 55 percent of people worldwide, according to Proctor & Gamble researcher James Schwartz, Ph.D. Although it does not usually cause complication, the National Institutes of Health warns that severe cases can lead to secondary infections, as well psychological distress and low self-esteem, if they are not controlled.
Definition
Dandruff is a skin condition that causes flaking, redness and itching of the scalp, according to the Mayo Clinic. Tom Dawson, Ph.D., a senior scientist with Proctor & Gamble, explains that it also makes affected area feel dry and tight. It is not dangerous and cannot spread to other people, though the flakes are visible in the hair and on clothing when they eventually fall from the scalp.
Causes
Dandruff has a variety of causes, the Mayo Clinic explains. They include dry skin, sensitivity to shampoo and hair styling products, oily skin and infrequent shampooing. A more serious form, called seborrheic dermatitis, is caused by a yeast-like fungus known as malassezia. Most people get dandruff from a combination of these risk factors, according to NIH.
Process
Most healthy adults have some malassezia growing on their scalps, according to the Mayo Clinic. It doesn't cause problems for the majority of people, but some get an overabundance of the fungus. It eats natural oils secreted by the hair follicles. Eventually this irritates the scalp and causes abnormal skin cell growth. The skin cells die and clump together with skin oil when they are shed, forming white or yellow dandruff flakes.
Considerations
Doctors do not know exactly why malassezia grows excessively on certain people, but several factors seem to contribute to the problem. The fungus thrives on people with naturally oily scalps and those with suppressed immune systems, the Mayo Clinic explains. People with Parkinson's disease and other neurological problems or certain hormonal changes are more prone to seborrheic dermatitis, as are those who are sick or under physical or emotional stress. Some people are more sensitive to the fungus, according to the Mayo Clinic, which boosts their dandruff risk.
Treatment
Dandruff caused by scalp fungus can be controlled with medicated shampoos, according to Dr. Betty Anne Johnson and Dr. Julia Nunley of the Commonwealth University in Virginia. They recommend daily shampooing with a product containing selenium sulfide, pyrithione zinc or ketoconazole. The shampoo should stay on the scalp for five to 10 minutes before rinsing to effectively control malassezia. It can be used twice weekly for maintenance once the dandruff improves.
