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Author: Dr Amy Stanway, Department of Dermatology, Waikato Hospital, Hamilton, New Zealand, 2004.
Psoriasis is a common skin condition, characterised by red scaly thickened patches (plaques). It often affects the scalp. Scalp psoriasis may occur in isolation or with any other form of psoriasis.
The back of the head is a common site for psoriasis, but multiple discrete areas of the scalp or the whole scalp may be affected. Scalp psoriasis is characterised by thick scale over well-defined, red thickened skin. The scale is often silvery white. Psoriasis may extend slightly beyond the hairline (facial psoriasis).
Scalp psoriasis, even though often adequately camouflaged by the hair, is often a source of social embarrassment due to flaking of the scale and severe 'dandruff'. Scalp psoriasis may not cause any symptoms at all or may be extremely itchy. It tends to be a chronic problem, lasting many years, although it often fluctuates in severity and extent.
In very severe cases, there may be some temporary mild localised hair loss, but scalp psoriasis does not cause permanent balding.
For information on trichoscopic (dermoscopic) findings, see trichoscopy of inflammatory conditions.
Sebopsoriasis is an overlap between psoriasis and another common skin condition, seborrhoeic dermatitis. Sebopsoriasis tends to have less silvery scale than psoriasis and more yellowish, greasy scale.
Pityriasis amiantacea is characterised by thick, yellow-white scales densely coating the scalp skin and adhering to the hairs as they exit the scalp. The scales are arranged in an overlapping manner like tiles on a roof or flakes of asbestos, hence the name. The underlying scalp skin may appear normal, aside from the scale, or can be reddened or scaly. Pityriasis amiantacea is often present without any apparent underlying cause but may be associated with psoriasis, seborrhoeic dermatitis or lichen simplex (another form of dermatitis).
Most patients with scalp psoriasis do not lose hair despite thick plaques. However, hair loss and localised bald patches (alopecia) can occur.
Scalp psoriasis associated with hair loss
Scalp psoriasis requires slightly different regimes from psoriasis affecting the skin elsewhere. This is due to hair, which makes the application of many topical products difficult and protects the scalp from the effects of ultraviolet light. Unfortunately, many scalp treatments for scalp psoriasis are messy and smelly. Most treatments will need to be used regularly for several weeks before a benefit is seen.
Special medicated shampoos can be purchased from the chemist.
The shampoos work best if rubbed into the scalp well, and left in for 5 or 10 minutes and then reapplied. They are safe for daily use but may irritate if applied more than twice weekly. If you dislike the smell of coal tar, try shampooing again with a favourite brand, and use a conditioner.
More severe cases require leave-on scalp applications.
Use the scalp preparation daily at first then as the condition improves, reduce the frequency. In many cases the scale soon builds up again, so the creams may have to be applied regularly to keep the scalp clear. Topical steroids are best used only 2-3 times weekly, long term to avoid complications.
Cutting hair short helps control scalp psoriasis, probably by making the treatments easier to apply, but is not appealing to everyone.
Phototherapy is effective for chronic plaque psoriasis but challenging to deliver to the scalp. Special targeted devices and UVB combs have been devised, and appear very helpful. In some cases, prolonged clearance has resulted from a course of treatment.
Intralesional corticosteroid injections and systemic therapy may be justified for patients with severe scalp psoriasis that has failed to respond to topical treatments and targeted phototherapy. These include acitretin, methotrexate, ciclosporin and biologic agents.
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