You spy a scatter of white flakes on your collar. Or you’ve got an itch that won’t quit, no matter how much you wash your hair. Dandruff isn’t glamorous, but it’s common: about half the world’s population has it.
An itchy, flaking scalp is rarely dangerous, but it can be annoying. Here’s what you need to know about what might be causing your flakes, what you can do about it, and when it’s time to get help.
What causes dandruff?
Dandruff is the mildest form of a condition called seborrheic dermatitis, a type of skin inflammation that usually affects the head, face or trunk. At its worst, this condition leads to patches of red skin covered in tiny, greasy scales. However, most people with dandruff have just minor scaliness and no redness, affecting only the scalp.
Experts still don’t know exactly what causes dandruff, and it’s likely there are various contributing factors. A yeast called Malassezia is a leading suspect, says James Pathoulas, an assistant professor of dermatology at the University of Minnesota medical school who specializes in hair and scalp disorders. Malassezia usually lives harmlessly on the scalp, but overgrowth has been linked with scalp inflammation.
It’s better to think about seborrheic dermatitis as a system in dysfunction rather than one organism causing trouble, according to Natasha Mesinkovska, an associate professor of dermatology at the University of California, Irvine. Scalp health comes down to a “trifecta” of factors, she says: the scalp’s microorganisms, its ability to keep those organisms out of deeper skin layers, and the skin’s immune response to them.
Who gets dandruff?
It’s not clear why some people get dandruff and others don’t. Genetics may play a role – at least 11 gene variants have been linked to the condition – as can hot, humid weather or a supercharged workout routine.
Hormones that drive oil production can also ramp symptoms up or down, beginning around puberty and changing during pregnancy or menopause.
What should I do about it?
If you’re seeing occasional light scale on your scalp with no significant redness or itch, over-the-counter dandruff shampoo can help. Zinc pyrithione, selenium sulfide and ketoconazole are the three most common active ingredients. They’re all equally good at lowering Malassezia populations, tamping down inflammation, and stopping the flakes.
Pathoulas recommends massaging the shampoo into your scalp, not just your hair, and leaving it on for a few minutes before rinsing. Use it three times a week; either your regular conditioner or a dandruff-specific product is fine. If you want to wash your hair on in-between days, your regular shampoo and conditioner are fine.
Ketoconazole and selenium sulfide can dry out hair and cause breakage, especially for dry, highly textured or coily hair, Pathoulas says. If that occurs, or you already rely on hair oils or leave-in conditioner, look for a gentler, sulfate-free zinc pyrithione formulation made for textured hair.
Go fragrance-free where you can, says Pathoulas. Fragrance is a common cause of scalp contact allergy, and it doesn’t have to be synthetic to cause a reaction: natural botanical fragrances can also wreak havoc.
Once symptoms clear, most people can taper dandruff shampoo use to once a week. If a shampoo that’s worked for months suddenly stops being effective, the yeast may have grown resistant to it, Pathoulas says. Switching to a different active ingredient for a while, then back again, can restore control.
When do I need to see a doctor?
If your scalp clears up with a medicated shampoo but flaking resumes within days of stopping, that’s a signal the underlying problem needs more attention, says Mesinkovska.
Thick, red, sharply defined plaques with silvery-white scale point toward psoriasis rather than dandruff, especially if you also have them on the elbows and knees. If the redness or scaly skin shows up elsewhere on your body, it could indicate an allergic reaction, depending on its location and your exposures, says Mesinkovska. Dandruff shampoo won’t have any effect on scalp flakes resulting from either of these conditions.
Hair loss or a burning or stinging sensation accompanying flakes is never normal, says Pathoulas. If you have these symptoms, a clinician should evaluate you for scarring alopecia.
If an evaluation shows that you just have ordinary dandruff but it isn’t responding to the basics, there are prescription options. The experts suggest ciclopirox shampoo, an antifungal with some antibacterial activity built in, and prescription-strength ketoconazole. Roflumilast is a newer option that you apply to your dry scalp as a foam.
Some researchers are trying to understand if manipulating the scalp’s bacterial populations might help – that is, adding good germs to outcompete any bad ones that might be causing problems. But that research is still in its early stages, so for now, experts aren’t recommending approaches like applying yoghurt or kombucha.
