Despite decades of research, doctors still don’t know what exactly causes dandruff—what dermatologists call seborrheic dermatitis. One known factor is having too much oil, or sebum, on the scalp. Another possible cause is the presence of the common yeast Malassezia globosa, which feeds on scalp oils.
But dandruff also can be triggered by psychological stress…low humidity…cancer…even certain medications, including drugs to treat hair loss. And while not shampooing frequently enough can foster flakes by allowing the buildup of oil on the scalp, shampooing too often can cause flakes by making the scalp too dry.
Whatever the cause, there are effective ways to prevent and stop the shedding of dead skin cells and the itching that characterize dandruff. Bottom Line Personal asked Brian J. Abittan, MD, assistant clinical professor of dermatology at Icahn School of Medicine in New York City, the most common questions about dandruff.
Does shampooing help or hurt?
For most people, shampooing three or four times a week is best. Shampooing every day can leave hair dry and the scalp flaky, though it may be fine for people whose hair is particularly oily. Long, hot showers tend to worsen dandruff—again, by drying the scalp. Best: Stick to brief lukewarm showers.
Should I use a dandruff shampoo?
Over-the-counter shampoos specifically designed to fight dandruff can be quite effective. Shampoos containing selenium sulfide or zinc generally are a good first choice. If those fail to bring relief from flakes after four to six weeks of use, try a shampoo containing salicylic acid, coal tar or the antifungal ketoconazole. After dandruff improves, you can keep using these shampoos less frequently for maintenance. Conditioners can help by moisturizing the scalp to minimize flaking.
Caution: Avoid hair products that contain alcohol—that includes many hairsprays—because alcohol can dry the scalp and contribute to flakes.
What about natural remedies?
You can certainly try natural topical remedies such as aloe vera and tea tree oil, but evidence supporting their effectiveness is limited…as is evidence for consuming fish oil, which contains omega-3 fatty acids that may soothe scalp irritation.
When should I see a doctor?
If dandruff is severe or persists for more than a few months despite self-care measures, it is time to visit a dermatologist, who can prescribe more potent treatments, including topical steroids. (Beware that topical steroids can cause skin thinning and lightening if used every day for more than a few weeks.)
