What is scalp psoriasis?
Psoriasis is a common skin condition, characterised by red scaly thickened patches (plaques). It ofen 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 silvery-white scale over well-defined red thickened skin. 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.
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 may be reddened or scaly. Pityriasis amiantacea is often present without any obvious underlying cause, but may be associated with psoriasis, seborrhoeic dermatitis or lichen simplex (another form of dermatitis).
Psoriatic hair loss
Most patients with scalp psoriasis do not lose hair despite thick plaques. However, hair loss and localised bald patches (alopecia) can occur.
- Psoriatic alopecia often affects psoriatic plaques (ie red, scaly, thickened skin)
- Scratching, combing, pulling off scale can contribute by pulling out clumps of hair
- The hair usually completely regrows after a period of time
- Scarring alopecia due to psoriasis is rare
- Generalised hair shedding can occur (telogen effluvium)
- Psoriasis may be associated with other autoimmune diseases including alopecia areata
- Treatment might lead to hair loss, for example due to the oral retinoid acitretin or biologics
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 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.
- Coal tar shampoos are suitable for most patients with scalp psoriasis.
- Ketoconazole, ciclopirox, zinc pyrithione and other antifungal shampoos are effective for dandruff and seborrhoeic dermatitis. They have varying effect in sebopsoriasis and psoriasis.
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.
- Alcohol-based, foam, gel or lotion forms of topical steroid and calcipotriol can reduce redness and itch but they don't lift scale very well. Use topical steroids intermittently; overuse results in more extensive and severe psoriasis.
- Salicylic acid and coal tar creams work much better, but are messy. Coconut oil compound ointment is a combination of coal tar, salicylic acid and sulphur and seems particularly effective. Leave on for at least an hour and shampoo off later. Most people rub the cream into the plaques at night and wash it off in the morning.
- Dithranol may be effective but is difficult to use and may be messy as it stains hair and fabrics.
Use the scalp preparation daily at first then as the condition improves, reduce the frequency. Unfortunately 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 difficult 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 agents may be justified for a few patients with severe scalp psoriasis that has failed to respond to treatments described above. These include acitretin, methotrexate, ciclosporin and biologic agents.