What is psoriasis?
Psoriasis is a skin condition that can cause sufferers much distress as a result of its unsightly appearance. It is thought to affect around 1–5% of the population worldwide and has a tendency to run in families. The condition is less common in sunny climates and in pigmented skins. It can appear at any time but often develops in the teens or 20s or later in life, in the 50s and 60s. Psoriasis can affect various areas of the body but in around 50% of people, it affects the scalp. The condition is unpredictable and symptoms may occur at irregular intervals. However, most people have mild, persistent symptoms for much of the time. Psoriasis is not infectious.
What are the symptoms of psoriasis?
In people with psoriasis, cells in the outer layer of the skin (the epidermis) are replaced at a faster rate than normal and there is inflammation in the epidermis and the layer of skin below (the dermis). This results in patches of psoriasis that often stand out from the skin; these raised patches are referred to as plaques. Plaques are often red and can be rounded in appearance. The surface of the affected skin is rough and scaly and can look silvery or shiny. Although the skin cells in these patches grow at a quicker rate than in normal skin, this rapid growth is thought to be a symptom of psoriasis rather than a cause. Psoriasis does not cause ill health in any other way and many sufferers are generally very healthy. In some cases, psoriasis plaques may not cause the sufferer any problems while in others they may cause mild itching. It is not usually painful and the main complaint is of its appearance.
Plaque psoriasis (psoriasis vulgaris) is the most common type of psoriasis. The parts of the body most commonly affected are the knees, lower back, elbows, shoulders and scalp. The face, hands and feet are rarely affected. Less common forms of the disease include guttate psoriasis (small spots), generalized psoriasis (all over the body), psoriasis of the nails, or pustular psoriasis.
What causes psoriasis?
Psoriasis is often an inherited condition but can also occur in people with no family history of the disease. If a parent has the condition it may be passed on to a child but this is not necessarily the case. For this reason, psoriasis is not considered to be a genetically inherited condition. Currently, there is no definite explanation for what causes psoriasis although it has been suggested that there are certain triggers that may cause it to develop, including injury, sunburn, HIV, beta-hemolytic streptococcal infection, emotional stress, alcohol and certain drugs. It is not an infectious condition but, occasionally, the skin may become infected and need treatment. There does not appear to be any connection between diet and psoriasis.