Psoriasis is a common medical condition that occurs when skin cells grow too quickly. The result can be seen as inflamed, thickened and scaly areas of skin. It can also affect other areas, such as the finger or toe nails.
In some cases the person may also have sore and inflamed joints at the same time. When this occurs, it is called psoriatic arthritis.
Psoriasis is not an infection and is not contagious. It cannot be spread by touch or being close to a person with psoriasis. Although it can look like a rash, it really isn't.
Psoriasis may seem to be only skin deep, but it does start inside the body - it is caused by over-activity of your body's immune system. The extra inflammation makes the skin cells grow and multiply too quickly. The body is not able to shed these excess skin cells, so they pile up on the surface of the skin.
The most common form of psoriasis appears as raised, red, itchy patches called plaques that are covered with a layer of flaky, silvery-white dead skin cells, called scales.