Common causes of an itchy scalp

Seborrhoeic dermatitis

Seborrhoeic dermatitis causes an itchy and sore rash on the scalp. The rash is usually red in colour, but can also appear as white scales. The scales have a tendency to flake off, so many people assume it is just dandruff.

The exact cause of this condition is unclear but it is thought to be due to an overgrowth of a common yeast skin organism. Seborrhoeic dermatitis tends to flare up in the winter months, and can be precipitated by stress. It runs in families and is more common in men. It is best treated with regular use of a medicated shampoo (either a traditional anti-dandruff shampoo or an anti-fungal shampoo such as ketoconazole, available from your pharmacist).

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Ringworm

Because of the name, many people assume that tinea capitis, or scalp ringworm, is caused by a parasitic worm. In fact, it's a common fungal infection. It can cause dry scaly patches within the hair or a classical red ring-like appearance. Sometimes the infection can cause damage to the hair and result in patches of hair loss.

It is contagious and may be passed on via hairbrushes, towels and even the backs of chairs. It usually needs to be treated with oral antifungal tablets. Antifungal shampoos do not tend to work, because the fungal infection spreads down into the hair follicles, where shampoos cannot reach.

Psoriasis

Psoriasis is a skin condition that often affects the scalp. About half of people with plaque psoriasis - the most common form of the condition - have psoriasis on their scalp as well. However, a few people develop psoriasis on their scalp with no plaques anywhere else on their bodies.

Like fungal infections, scalp psoriasis causes a dry, scaly itchy rash and can sometimes be tricky to distinguish from other scalp conditions. It typically affects the hairline at the back of the head and can cause quite marked shedding of heavy 'dandruff'.

It is usually treated with a combination of shampoos, scalp applications and sometimes more specialist treatments. The first-line treatment for scalp psoriasis is often a coal-tar based shampoo. Topical steroid treatments are recommended more often for psoriasis affecting the scalp rather than other parts of the body.

Head lice

Head lice don't just affect children! The lice are small grey-brown insects that live on the scalp. They are most commonly spread by head-to-head contact, and can cause itching if your scalp is sensitive to the saliva or faeces of the lice. Over-the-counter head lice treatments are readily available from your pharmacist.

Dandruff

Pityriasis capitis, or dandruff, is the most common cause of a dry flaky scalp and affects many of us. It is caused by dead skin cells being shed more rapidly than usual and, although it is not harmful, can be irritating and embarrassing. Excessive use of some hair products can lead to dandruff. Avoiding triggers and using anti-dandruff shampoos usually solve this problem.

If you are struggling with itchy or sore patches on your scalp, then make sure you see your GP for further advice.