Quick answer: Seborrhoeic dermatitis is a common scalp condition that causes greasy, yellowish flakes, redness and itching. It's linked to a yeast that lives on everyone's skin, and it flares with stress, cold weather and illness. It isn't caused by poor hygiene and it isn't catching. It's controlled, not cured: a medicated shampoo (ketoconazole, coal tar or salicylic acid) used properly for a few weeks, then regularly to keep it away. See your GP if it hasn't improved after four weeks, or if your scalp is very red, sore or swollen.
"It's just dandruff," people tell me, usually while scratching. Then they list the five anti-dandruff shampoos they've tried, none of which worked for more than a week.
Here's the thing. Ordinary dandruff is dry, white, powdery flakes with a bit of itch. If what you've got is greasy, yellowish, sticks to the scalp in patches, and sometimes shows up around your eyebrows, the sides of your nose or behind your ears too, you're probably not dealing with ordinary dandruff. You're dealing with seborrhoeic dermatitis, and it needs a slightly different approach.
I see this all the time at Tess Hair and Scalp Clinic in Belfast, often in people who've been quietly battling it for years. So let's go through it properly.
What seborrhoeic dermatitis actually is
Seborrhoeic dermatitis (say it "seb-or-ay-ick") is an inflammatory skin condition that affects the oily areas of the body, and the scalp is the oiliest of all. The NHS dandruff page lists it as one of the conditions that can cause flaking, describing "scaly, itchy and red patches on skin on scalp, face and other areas of the body".
It's thought to involve a yeast called Malassezia that lives on everyone's skin. In some people the skin over-reacts to it, causing inflammation, extra oil, and the greasy flaking you see. Why some people react and others don't isn't fully understood.
Two things it is not: it is not caused by being unclean (the NHS is clear that dandruff "is not caused by poor hygiene"), and it is not something you can pass to anyone else.
Dandruff or seborrhoeic dermatitis? How to tell
Flakes. Ordinary dandruff: Small, dry, white, fall freely. Seborrhoeic dermatitis: Larger, greasy, yellowish, stick to the scalp.
Scalp. Ordinary dandruff: Looks normal, mild itch. Seborrhoeic dermatitis: Red or pink patches, often itchy, sometimes sore.
Where. Ordinary dandruff: Scalp only. Seborrhoeic dermatitis: Scalp, plus eyebrows, sides of nose, behind ears, chest.
Pattern. Ordinary dandruff: Fairly steady. Seborrhoeic dermatitis: Comes and goes, flares with stress, cold weather, illness.
Response to shampoo. Ordinary dandruff: Improves with regular anti-dandruff shampoo. Seborrhoeic dermatitis: Needs a medicated shampoo used in a specific way, and comes back if you stop.
If you tick the right-hand column, keep reading.
What makes it flare
Most people with seborrhoeic dermatitis have good spells and bad spells. The common triggers I see in clinic:
Stress and tiredness. The classic one. Exam season, a new baby, a bad month at work.
Cold weather and central heating. Belfast winters are not kind to scalps. The NHS notes that cold weather can make dandruff worse, and the same goes for this.
Being run down or unwell.
Heavy, oily hair products left on the scalp, especially under hats or in protective styles that are kept in for weeks.
Infrequent washing. Washing doesn't cause it, but leaving oil and yeast on the scalp for a week gives it a head start.
What actually helps
1. The right shampoo, used the right way
This is where most people go wrong. They buy the right product and use it like a normal shampoo, which means it's on the scalp for about twelve seconds.
The NHS recommends looking for a shampoo containing one or more of ketoconazole, coal tar or salicylic acid. You can buy these from a pharmacy or supermarket without a prescription. Ketoconazole is the one I usually suggest first for greasy, yellowish flaking, because it targets the yeast directly.
The NHS instructions for ketoconazole shampoo are specific, and worth following to the letter:
Use it twice a week for 2 to 4 weeks until your symptoms have cleared.
Leave it on for 3 to 5 minutes before rinsing. This is the step everyone skips. Set a timer.
Then use it once every 1 to 2 weeks to stop it coming back.
That last step is the one that matters most. Seborrhoeic dermatitis is controlled, not cured. Stop completely and it usually returns within a few weeks.
2. Keep washing
If your scalp is greasy and flaky, washing more often, not less, helps. Use a gentle shampoo on the days in between your medicated washes. Make sure you're washing the scalp, not just the hair: fingertips, not nails, working across the whole head.
3. Lighten up on products
Heavy oils, butters, pomades and leave-ins sitting on the scalp feed the problem. Keep oils on the lengths, not the roots, while you're getting it under control.
4. Give it four weeks before you judge
The NHS advises using an anti-dandruff shampoo for up to four weeks to see if it helps, and trying a different one if it doesn't. Switching every five days means nothing gets a fair trial.
5. Don't scratch, and don't pick
I know. But picking at the patches makes them sore, and sore patches can get infected. A cool rinse at the end of your wash helps with the itch.
What about hair loss with seborrhoeic dermatitis?
A lot of people ask whether it's making their hair fall out. The condition itself doesn't usually destroy follicles, but an inflamed, itchy scalp isn't a good environment for growing hair, and constant scratching can snap hairs and increase shedding. Most people find that once the scalp calms down, the shedding settles too.
If the shedding is heavy, or carries on after your scalp has cleared, there's probably something else going on alongside it. Our post on the ten common causes of hair falling out is a good next read.
When to see your GP
The NHS says to see a GP if:
your dandruff hasn't improved after at least four weeks of using an anti-dandruff shampoo
it's severe or very itchy
your scalp is red or swollen
you have flaky, itchy patches on your face or body as well
A GP can check whether it's seborrhoeic dermatitis, psoriasis, eczema or something else, and can prescribe stronger treatments such as a short course of a steroid scalp application if it's very inflamed.
When a trichologist helps
A trichologist can look at your scalp up close with a magnifying camera, tell you whether what you're seeing fits seborrhoeic dermatitis, psoriasis or product build-up (they're easy to confuse), and build a washing and product routine that actually fits your hair type. Our in-clinic scalp treatments can help calm and clear a flaky scalp, and we'll always tell you if you need your GP instead.
Common mistakes
Treating it as dry scalp and piling on oil. Greasy flakes plus more oil is a bad combination.
Rinsing the medicated shampoo off straight away. It needs 3 to 5 minutes to work.
Stopping as soon as it clears. Keep up the once-a-fortnight wash.
Washing less because the scalp is "sensitive". The yeast loves that.
Scrubbing with nails or harsh scalp scrubs. It's inflamed skin. Be kind to it.
Frequently asked questions
What does seborrhoeic dermatitis look like on the scalp?
Greasy, yellowish or white flakes stuck to red or pink patches of scalp, often itchy. It can also appear on the eyebrows, sides of the nose, behind the ears and on the chest.
Is seborrhoeic dermatitis the same as dandruff?
Mild dandruff and seborrhoeic dermatitis are related, but seborrhoeic dermatitis involves visible inflammation (redness) and greasier flaking, and it tends to come and go.
Can seborrhoeic dermatitis be cured?
Not permanently, but it can be controlled well with the right shampoo used regularly. Most people have long clear spells.
Does seborrhoeic dermatitis cause permanent hair loss?
Usually not. Shedding can increase during a flare, but it typically settles once the scalp is calm.
Which shampoo is best for seborrhoeic dermatitis?
The NHS recommends shampoos containing ketoconazole, coal tar or salicylic acid. Ketoconazole is a good first choice. Ask a pharmacist if you're unsure.
Flaky, itchy and fed up?
Book a hair and scalp analysis with Theresa at Tess Hair and Scalp Clinic, 77a Botanic Avenue, Belfast, or call 028 9096 4731. We'll look at your scalp properly, tell you what it is, and sort out a routine that keeps it calm. See our scalp treatments and prices here.
About the author: Theresa Anthony is the trichologist at Tess Hair and Scalp Clinic, 77a Botanic Avenue, Belfast BT7 1JL, where hair loss treatment and a full hair salon sit under one roof.
Sources: NHS: Dandruff · NHS: How and when to use ketoconazole
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