It may range from just a few spots anywhere on the body to large areas of involvement. It is not contagious or spreadable from one part of the body to another or from one person to another. There is no blood test for psoriasis. The diagnosis is made by observation and examination of the skin. The exact cause of psoriasis is unknown, but hereditary and genetic factors are important.
Psoriasis runs in families.
This does not mean, however, that every child of a parent with psoriasis will develop psoriasis, but it is common that somewhere down the line psoriasis will appear in families. Psoriasis is not caused by allergies, infections, dietary deficiencies or excesses, or nervous tension. If it is widespread it can certainly cause a great deal of skin discomfort and emotional embarrassment, and can affect job and leisure time activities. Fortunately most people who have psoriasis only have a small amount and while it certainly can be a nuisance, it does not alter the lifestyle. In about 10 percent of people with psoriasis there can develop a form of arthritis called psoriatic arthritis.