Psoriasis is a skin condition in which skin cells reproduce too quickly. It affects around 2% of people in the UK.
It can start at any age, but most often develops between 11 and 45 years old, often at puberty.
Skin cells have a life-cycle. Your body produces new cells in your lowest skin level and these skin cells gradually move up through the layers of your skin until they reach the outermost level. Then they die and flake off. This whole process normally takes around 21 to 28 days.
In psoriasis this process is speeded up so it only takes two to six days. As a result, cells build up rapidly on the surface of the skin, causing red, flaky, crusty patches covered with silvery scales.
These patches are then shed easily. It can occur on any part of your body although it's most commonly found on the elbows, knees, lower back and the scalp. It can also cause itching and burning.
The condition is not contagious and most people are affected only in small patches of their body.