Psoriasis is a chronic disorder of the skin, which typically consists of red patches covered by silvery-white scales. These red scaly patches are usually found on the elbows, knees, lower back and scalp although not infrequently patches appear elsewhere including the nails. When psoriasis involves the groin, armpits, genital area and beneath the breasts it tends to be less scaly and have a glazed appearance. Psoriasis infrequently affects the face. It does not cause scarring and rarely results in hair loss.
Psoriasis is very common. Approximately 2% of adults have psoriasis. Its exact cause is unknown but the result is skin, which grows about seven times more quickly and thickly than usual. It is thought to be due, at least in part, to an abnormal immune reaction against some component of the skin. Genetic factors play a part; only some families develop the condition, and about half those affected know of someone else in the family with it.
The rash often seems to start after some sort of trigger factor. This may be emotional stress, skin injury (cuts and scratches for example), a streptococcal sore throat, hormones (it often first occurs at puberty), or rarely, certain medications. These factors should be avoided whenever possible by people with Psoriasis. Excessive alcohol aggravates Psoriasis. It is not an allergy, nor is it infectious to others.
Psoriasis may improve or get worse during pregnancy. It does not have any harmful effect on either mother or child.
The extent of Psoriasis varies, and fluctuates even without treatment. It may even disappear completely. However, the predisposition to develop Psoriasis remains, so the rash may recur at a later date even when it has been absent for years.
Treatment of Psoriasis
There are a variety of treatments for psoriasis, and new ones are under development.
Sunshine
Sunshine may help to clear psoriasis; in many people it improves dramatically during sunny holidays. Take care, as psoriasis may develop in areas of sunburn, and fair skin exposed to ultraviolet radiation becomes prematurely aged and may develop skin cancer.
Baths
Soaking in warm water with a bath oil or tar solution can soften the psoriasis and lift the scale. Bland soaps or soap substitutes are useful; detergents and antiseptics are not necessary and may irritate.
Emollients
Even if no medicated preparations are applied, the psoriasis should be kept soft with moisturizing creams to prevent it cracking and becoming sore. Vaseline, emulsifying ointment and Sorbolene Cream are among suitable preparations.
Occlusive dressings
Patches of psoriasis, which are limited in extent, may improve with occlusive dressings i.e. waterproof adhesive dressings.
Scalp Care
Special medicated shampoos can be purchased from the chemist. Most contain coal tar. Ketoconazole shampoo is an effective preparation for dandruff, and is sometimes helpful for 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. Some people dislike the smell - try shampooing again with a favourite brand, and use a conditioner.
More severe cases require scalp applications. Alcohol based products are easiest but can sting. Steroid lotions can reduce itch but don't lift scale very well. Creams with salicylic acid and coal tar work much better, but are messy. They should be left on for several hours and shampooed off later. Most people rub them in at nighttime, washing them off in the morning.
Unfortunately in many cases the scale soon builds up again, so the creams may have to be applied every day to keep the scalp clear.
Crude coal tar
Coal tar has been used for many years. In the "Goeckerman" regime in hospital, it is applied twice daily to the patches after exposure to ultraviolet light. The psoriasis clears in 4 - 6 weeks and may stay away for months.
This intense regime is inappropriate for home use. Instead, refined coal tar is used in various cream, ointment, gel and stick bases. Coal tar may sting or even aggravate the psoriasis, but most find it helpful.
Don't apply coal tar or pine tar immediately before sunbathing - the result could be a severe burn.
Dithranol
Dithranol is applied twice daily in hospital in the "Ingram" regime. It works faster than coal tar, but is more difficult to use. Very fair skinned subjects don't tolerate it. It must be applied very accurately so it is only suitable for large patches. At home
it's best to use "short contact Dithranol". Apply it accurately to the patches of psoriasis for 10 minutes only. It stains the skin a brown colour and can irritate.
Topical steroids
Patients often prefer to use Topical Steroids, as these are clean and soothing. Weak ones like hydrocortisone are suitable for large areas or delicate places like face, armpits and groin (often combined with an antifungal agent to combat thrush).
Stronger topical steroids need to be used with care. They are inappropriate for large areas and should only be used for limited periods. There are a number of problems with them - for example they thin the skin (causing broken capillaries and stretch marks) and can result in long-term aggravation of psoriasis.
The most powerful topical steroid preparations are most effective (and result in most side effects). Adverse effects can be avoided if they are applied daily for no more than two weeks out of every two months, or twice weekly long-term. Don't use them on face, armpits or groin, and never use more than 50 g a month without specialist advice.
Vitamin D-like Compounds
Calcipotriol ointment/cream is an effective and safe treatment for Psoriasis. A scalp preparation has recently been released. Calcipotriol has vitamin-D-like activity and is suitable for mild to moderate cases. No more than 100g should be used each week.
Twice daily application sometimes clears the Psoriasis within 6 to 8 weeks. More often, calcipotriol ointment lessens the itching, scaling, thickness and redness of the plaques. One-in-five subject’s experiences irritation from this preparation, but this may lessen with continued use. A facial rash can occur.
Ultraviolet Radiation - UVB
UVB treatment is available at some hospitals and private specialists' rooms, and is most useful during the winter months. It is indicated for moderate cases in combination with topical agents or acetretin. A six week course three times weekly often results in substantial improvement or clearance. UVB adds to sun exposure in causing aging of the skin and skin cancer, so it should not be continued indefinitely.
Ultraviolet Radiation - PUVA
Psoralens plus long wave Ultra Violet Aradiation, known as photochemotherapy or PUVA, is more effective than UVB. It can cause burning and skin cancer too but is a popular treatment because of its ease and efficacy. In New Zealand, it is only available under specialist supervision in the main centers.
Oral medications
At present oral medication is reserved for those with very extensive psoriasis (when 40% or more of the body surface is affected) or when it significantly interferes with function, eg. psoriasis on the palms preventing work, or on the feet preventing walking. All have potential side effects and risks which need to be carefully explained.
Methotrexate
Methotrexate tablets are taken once a week and usually result in dramatic improvement. Methotrexate occasionally causes nausea, and regular blood tests are necessary. It can damage the liver if taken long term, and alcohol should be avoided.
Acetretin
This vitamin A-like compound results in slow improvement in most cases. Unfortunately it has some nuisance side effects including dry lips, peeling palms and soles, thinning hair, tiredness and muscle pains. The side effects are dose-related but blood tests are usually necessary. It too can cause liver damage. Pregnancy must be strictly avoided whilst on acetretin and for at least 3 years afterwards.
Cyclosporin
This is an immune suppressive agent reserved for the most severe cases of psoriasis. It is very effective but may result in raised blood pressure and kidney damage so must be carefully monitored.
