Dandruff: what causes it and which dandruff shampoo works

Everyone knows what dandruff looks like on a dark jacket. Fewer people know what it actually is. Dandruff is made of flakes of the skin's outer layer coming away from the scalp. White, grey or yellowish, they spoil the look of the hair, itch, and make hair greasy faster.

The good news is that dandruff is one of the most common and most manageable scalp conditions. The bad news is that it tends to come back, so it pays to understand the cause rather than wash it away once.

What causes dandruff

Dandruff appears when the outer layer of skin renews itself too fast and the oil glands are overactive. A yeast called Malassezia lives on every scalp and feeds on skin oil. In some people the by-products irritate the skin: cells turn over faster, clump together and shed as visible flakes.

Oil production rises at puberty, which is why dandruff often starts in the teens. Other things make it worse:

• an oily scalp and infrequent washing, which lets oil build up;
• stress and tiredness;
• cold, dry winter air and central heating;
• the wrong shampoo or one that is poorly rinsed, and residue from spray, mousse, gel and wax;
• a sensitive scalp and some skin conditions.

The more severe form is seborrhoeic dermatitis: the skin is red, the flakes are greasy and yellowish, and the eyebrows, the sides of the nose and the skin behind the ears may flake too. That is a matter for a doctor, not for cosmetics.

Dandruff or dry scalp: how to tell

The two look alike but need opposite care: a dry scalp wants gentleness and moisture, dandruff wants an antifungal shampoo.

Sign	Dandruff	Dry scalp
Flakes	Larger, oily, white or yellowish	Small, dry, white
Scalp	Oily, sometimes red	Tight and dry
Hair	Gets greasy quickly	Dry, static
Gets worse	With less washing and under stress	In winter and with frequent hot washing
What helps	Dandruff shampoo	A mild shampoo, less hot blow-drying

A third possibility is neither: styling product residue. It falls in flakes, but the scalp neither itches nor gets greasy. A clarifying shampoo sorts it out.

Which dandruff shampoo works

"Anti-dandruff" on the bottle tells you little. What matters is the active ingredient.

Active ingredient	What it does	Notes
Ketoconazole	Suppresses the yeast	Sold in pharmacies; often the first choice when cosmetic shampoos fail
Selenium sulfide	Suppresses the yeast, slows cell turnover	Poorly rinsed, it can alter the shade of blonde or coloured hair
Piroctone olamine, climbazole	Suppress the yeast	The usual actives in cosmetic shampoos sold in Europe
Zinc pyrithione	Suppresses the yeast	Still common in the US; banned in cosmetics in the EU since March 2022
Salicylic acid	Loosens built-up flakes	Can be drying; follow with conditioner
Coal tar	Slows cell turnover	May stain light hair; makes the scalp more sensitive to sun

That European ban explains a common complaint: if your old favourite "is not what it used to be", the formula was probably changed.

How to use dandruff shampoo so that it works

1. Apply it to the scalp, not the hair. Massage with your fingertips; do not scratch.
2. Leave it on. Most shampoos need about five minutes for the active ingredient to act. Check the label.
3. Rinse well and use your normal conditioner on the lengths.
4. Be regular. Two or three times a week to begin with, then once a week to keep it away.
5. Judge after three to four weeks. If it does not help, switch to a different active ingredient rather than another brand of the same one.

Washing too rarely for fear of "drying out" is another mistake. On an oily, flaking scalp, oil builds up and the yeast has more to feed on.

When dandruff needs a doctor

• you have used dandruff shampoo for a month and nothing has changed;
• the dandruff is very heavy or the scalp is very itchy;
• the scalp is red, swollen or sore;
• flaky patches have appeared on the face or body;
• your immune system is weakened by illness or treatment.

Psoriasis, eczema, a fungal scalp infection and an allergy to hair dye can all look similar, and shampoo will not fix them.

What else you can do yourself

• Eat a balanced diet and manage stress: flare-ups often follow tired, stressful weeks.
• Use fewer styling products near the roots and less hot air.
• Keep brushes, combs, towels and pillowcases clean.
• Do not use several medicated shampoos at once.

Home remedies are popular, and it is fair to say most are untested. The best studied is tea tree oil: small studies suggest a shampoo containing it can reduce dandruff, but the neat oil often irritates and can cause allergy. Oil masks can make an oily, flaking scalp worse, because the yeast feeds on oil. Lemon juice irritates and dries the scalp.

Dandruff before a shoot, a casting or a big evening

For models the scalp is part of the job: a dark jacket or a black dress shows every flake. This is what we do before filming or a casting.

• Start the dandruff shampoo at least two weeks ahead, not the night before.
• Do not experiment with new masks or oils the day before.
• Dry hair with warm, not hot, air and keep spray away from the roots.
• Carry a lint roller and a wide-tooth comb.

How models look after skin and hair before castings is part of model training. If you would like advice on a cut and routine that suit your hair and face, see image consultation. Read next: hair loss, causes and what really helps. Whether your hair will frizz today is on the hair weather page.

Frequently asked questions

Is dandruff contagious?

No. The yeast linked to dandruff lives on everyone's scalp. Dandruff appears when the skin reacts to it, so you cannot catch it from someone else.

Is dandruff caused by poor hygiene?

No, but washing rarely makes it more visible, because oil and shed cells build up.

How do you get rid of dandruff fast?

Not in a day. With a dandruff shampoo two or three times a week, improvement usually shows within two to four weeks. After that, use it once a week to keep dandruff from returning.

Does dandruff cause hair loss?

Dandruff itself does not. Hard scratching can damage hair, though, and seborrhoeic dermatitis sometimes comes with other scalp conditions. If your hair is thinning, talk to a doctor.

How often should you wash your hair if you have dandruff?

Often enough that the scalp is not oily: for most people every day or every other day. Use the dandruff shampoo two or three times a week and a mild shampoo in between.

Can you use dandruff shampoo on coloured hair?

Yes, but some ingredients, especially selenium sulfide and coal tar, can change the shade of blonde or dyed hair. Pick one labelled safe for coloured hair and rinse well.