Dandruff

Dandruff is a scalp condition that causes flaking and itching. The skin on your scalp sheds faster than it should, and those extra cells clump together into visible flakes.

The flakes are usually white to yellow and fairly large. A useful detail: dandruff flakes often have small "hair holes" in them, because the flake formed around a hair. Dry scalp flakes don't have that.

Dandruff is not harmful. It can't spread to other people, and it doesn't damage your hair. But the flakes on dark clothing and the persistent itch bother a lot of people, and that's a legitimate reason to treat it.

It's a long-term condition. It comes and goes, often worse in winter and during stressful periods. The goal is control, not cure.

White to yellow flakes. Larger than dry-scalp flakes, and often with small holes where hair grew through.

Mild to moderate itching. Usually annoying rather than severe. If the itch is intense or burning, consider scalp psoriasis instead.

Flakes on clothing. Especially noticeable on dark shirts and jackets.

An oily or greasy scalp. Many people with dandruff have an oilier scalp.

Little to no redness. If you lift a flake and the skin underneath is red and raised, that points toward psoriasis or seborrheic dermatitis, not simple dandruff.

The exact cause isn't fully settled, but the leading explanation involves a yeast called Malassezia.

Malassezia lives on nearly everyone's scalp — it's normal, and it isn't an infection. It feeds on the oils your scalp produces. In some people, the immune system reacts to the yeast, or to the byproducts it creates. That reaction causes irritation, faster skin shedding, and flaking.

This explains why antifungal shampoos work so well. They aren't curing an infection; they're reducing the amount of yeast so your scalp stops reacting to it.

It also explains why dandruff comes back when you stop treating it. The yeast is still there. It's a normal part of your scalp. Treatment keeps its numbers down, but it never leaves for good.

Stress. A reliable trigger for many people.

Cold, dry weather. Winter is usually worse. Sunlight tends to help, which is part of why summer is often better.

Washing too little (if your scalp is oily). Oil feeds the yeast. If your scalp is oily, washing more often helps.

Washing too much (if your scalp is dry). Over-washing strips the scalp and worsens irritation.

Product buildup. Gels, waxes, and dry shampoos can build up and irritate the scalp.

Diet. The link is not well proven, but low zinc and B vitamins may play a role.

Hard water. Can dry and irritate the scalp, making things worse. It isn't a direct cause.

Dandruff is usually diagnosed by looking. A dermatologist will part your hair, look at the scalp and the flakes, and check whether the skin underneath is red or raised.

They'll also check your eyebrows, the sides of your nose, and behind your ears. If those areas are involved, it's more likely seborrheic dermatitis than plain dandruff.

No test is usually needed. If it doesn't respond to treatment, a dermatologist will look more carefully for psoriasis, a fungal infection, or seborrheic dermatitis.

Match the shampoo to your scalp. This is the single most useful thing to get right:

• Mild flakes → zinc pyrithione or tea tree oil
• Persistent flakes → ketoconazole or selenium sulfide
• Oily scalp → selenium sulfide or tea tree oil
• Thick flakes → salicylic acid or coal tar
• Sensitive scalp → tea tree oil or apple cider vinegar

Start with a mild option. If it isn't working after a couple of weeks, step up to an antifungal.

Use it correctly. Apply to the scalp, not the hair. Leave it on for several minutes — the active ingredient needs contact time. Rinsing right away wastes it.

Adjust how often you wash. Oily scalp: shampoo daily. Dry scalp: shampoo less often. This is the opposite advice for opposite scalps, and people often get it backwards.

Be patient. Dandruff shampoos take 1–2 weeks to show real improvement.

Other things that help: manage stress, get a little sunlight on your scalp, cut back on styling products, and eat foods with zinc and B vitamins.

For mild flakes
Zinc pyrithione (Head & Shoulders, Dove Dandruff, Biolage) — gentle enough for regular use and sensitive scalps. Tea tree oil shampoos are a good natural alternative with a cooling feel.

For persistent or moderate flakes
Ketoconazole 1% (Nizoral) — a strong antifungal. Use 1–2 times weekly. Selenium sulfide 1% (Selsun Blue, Head & Shoulders Clinical) — fights yeast and cuts scalp oil. Use 2–3 times weekly.

For an oily scalp
Selenium sulfide or tea tree oil. Both reduce oil as well as flakes.

For thick flakes
Salicylic acid (Neutrogena T/Sal, Ouai Dandruff) exfoliates and breaks up buildup. Coal tar (Neutrogena T/Gel, Denorex) slows skin cell growth. Coal tar smells strong and can stain.

For a sensitive or red scalp
Tea tree oil or apple cider vinegar shampoos. Gentler, and they calm irritation while reducing flakes.

A tip: rotating between two shampoos with different active ingredients often works better than using one indefinitely.

If OTC shampoos aren't working after several weeks of correct use, see a dermatologist. Persistent "dandruff" is often actually seborrheic dermatitis or scalp psoriasis, which need different treatment.

Ketoconazole 2% shampoo. The prescription-strength version of Nizoral. Used 2–3 times weekly during flares.

Ciclopirox 2% shampoo. A prescription antifungal. Also used 2–3 times weekly.

Clobetasol lotion or solution. A strong topical steroid for itching and inflammation. It works well, but prolonged use thins the skin. Use only as directed and in cycles.

See a dermatologist if:

• OTC dandruff shampoo hasn't helped after 2–4 weeks of correct use
• The skin under the flakes is red, raised, or thick
• Flaking has spread to your eyebrows, the sides of your nose, or behind your ears
• The itch is severe, burning, or keeping you up
• You're losing hair
• The scalp is sore, crusted, or oozing

Any of these suggest it's something other than simple dandruff — and something else needs different treatment.

Dry scalp. Small, white, dry flakes. Mild itch. No redness. Worse in cold weather or with harsh shampoo. The fix is moisture and a gentler shampoo — antifungal shampoo won't help and may make it worse.

Seborrheic dermatitis. Think of it as dandruff's more inflamed relative. Greasy yellowish flakes that cling to the skin, visible redness, and it often affects the eyebrows and the sides of the nose too. Needs antifungal shampoo plus prescription anti-inflammatory treatment.

Scalp psoriasis. Thick, silvery-white scale on red, raised skin. Itch is moderate to severe, sometimes burning. It crosses the hairline onto the forehead, neck, and behind the ears. Dandruff stays on the scalp.

Head lice. Not flakes at all — nits are eggs glued to hair strands and won't brush off. The itch is intense, especially behind the ears and at the neckline. If you can't flick it off the hair, it isn't dandruff.

The quickest test: try to move the flake. Dandruff and dry scalp flakes come free easily. Nits do not.