Psoriasis
What is it?
Psoriasis is a skin disorder which takes its name from the Greek word for 'itch', and usually appears as inflamed swollen skin lesions covered with silvery white scales. It commonly affects the scalp, knees, elbows, hands and feet. Psoriasis affects over six million people in the USA, particularly those between the ages of 15 and 35. The disorder comes in many forms which differ in severity, duration, location and in the shape and pattern of the lesions.
Skin cells in a normal growth pattern are created in the basal cell layer and move up to the outermost layer, where they are shed at about the same rate as new ones are produced. This process normally takes about 28 days. When skin is injured, the cells are produced at a faster rate to replace and repair the wound. There is also an increased blood supply and localized inflammation. In psoriasis, the growth and maturation rate of skin cells is increased and the whole process can occur in as little as three to six days. The skin cannot shed the dead cells fast enough and they build up and form scaly lesions.
The cause of psoriasis is unknown, although it may have a genetic component and may be an autoimmune disorder. A trigger, such as a medication or an injury to the skin, may cause psoriasis to develop. Nutritional factors, stress and psychological factors may also play a part. It is common for a flare up of symptoms to accompany an infection, especially a respiratory one. Environmental factors such as stress, and climate (usually cold) are important in some patients. About a third of patients have spontaneous remissions of their disease. Some cases are associated with severe arthritis, called psoriatic arthritis.
Treatment of psoriasis
Although there is no cure, there are several treatments for psoriasis. Therapy aims to reduce inflammation and slow down the rapid cell division. Treatment is based on the severity of the disease and the health, lifestyle and age of the person being treated.
Each person may benefit from a different therapy or combination of therapies. Therapies for mild psoriasis include exposure to sunlight, coal tar medications, anthralin, and steroids; either topical, injected or oral. Other treatments include the drugs, methotrexate and cyclosporin; and medically supervised administration of ultraviolet light with or without the drug, psoralen. Many of these treatments have adverse side effects.
Vitamins, minerals and psoriasis
Vitamin D derivatives
Synthetic vitamin D analogs known as calcipotriene and calcipotriol are used to treat psoriasis. These drugs affect immune response and skin cell proliferation and differentiation. Treatment with calcipotriene results in decreased redness, scaling and thickness of skin plaques. Irritant dermatitis is a common side effect of calcipotriene, especially when it is applied to the face. Careful patient monitoring is recommended because alterations in calcium metabolism have been reported to occur with use of calcipotriene. Calcipotriol may not have adverse effects on calcium metabolism and still has the beneficial effects against psoriasis.1 Ordinary vitamin D is not particularly effective in treating psoriasis.
Vitamin A derivatives
Vitamin A levels may be lower in psoriasis sufferers. The vitamin A derivatives, etretinate and isotretinoin, are widely used in psoriasis. Etretinate in combination with ultraviolet B and psoralen-ultraviolet A (PUVA) has shown beneficial effects. Vitamin A-derivative drugs help to normalize skin development by reducing the increased growth, turnover and keratinization of skin which occurs in the disorder.
However, long-term administration of vitamin A derivatives may lead to toxic effects, including headaches, inflammation of the lips, conjunctivitis, photosensitivity, and arthritis and bone abnormalities. These drugs can cause birth defects if taken during pregnancy and should also be avoided by breastfeeding women.
Zinc
Zinc metabolism may be abnormal in psoriasis, and copper-to-zinc ratio may also be high. There may also be a relationship between the total body area covered by the lesions and the plasma zinc level; those with more widespread lesions having lower levels than those with less.2 Oral zinc sulfate may be useful in the treatment of psoriatic arthritis, which accompanies the skin disease in approximately 10 to 20 per cent of cases.3
Selenium
Selenium levels may be low in psoriasis and this may affect the immune system. A 1993 study showed improvement in some measurements of immune system effectiveness when selenium-rich yeast was given to psoriasis patients.4 Blood levels of the selenium-containing enzyme, glutathione peroxidase, may be low in psoriasis sufferers. In one study, 50 patients with low glutathione peroxidase levels were treated with tablets containing 0.2 mg selenium and 10 mg vitamin E.5 The glutathione peroxidase levels increased slowly within six to eight weeks of treatment, and some improvement in symptoms was seen. However, other studies have not shown benefits with selenium supplements.6
Essential fatty acids
Essential fatty acid supplements may be beneficial in psoriasis sufferers. Analysis of blood and fat tissue has shown that the amount of anti-inflammatory alpha- linolenic acid decreases, while the level of arachidonic acid, which has inflammatory effects, increases. These changes may be more pronounced in patients with severe psoriasis than in those with a milder form of the disease.7
The results of a 1993 study suggest that eating oily fish may help reduce the symptoms of psoriasis.8 Some small studies suggest that fish oil supplementation may be beneficial in psoriasis. In a 1998 study, researchers from several European centers treated 83 patients with either a with either an omega-3 fatty acid-based lipid emulsion or a placebo. There were significant improvements in symptoms, as assessed both by the patients and the researchers.9 Topical fish oils have also shown some beneficial effects.10 Essential fatty acid supplements also help to reduce the toxicity of immune suppressant and vitamin A-derivative drugs.11
Herbal medicine and psoriasis
Herbal treatment of eczema and psoriasis involves the use of blood cleansing remedies and diuretics such as figwort (Scrophularia nodosa), cleavers (Galium aparine), nettles (Urtica dioica), burdock (Arctium lappa), red clover (Trifolium pratense) and yellow dock (Rumex crispus). Liver herbs, such as Oregon grape root (Mahonia aquifolium), may be used to improve detoxification. Other remedies, such as chickweed (Stellaria media), can be used to reduce itching while others act as antiseptics and anti-inflammatories. Nervine relaxants are sometimes used to help treat stress associated with eczema.