Psoriasis is a common, chronic, autoimmune disease that causes dry, red, scaly patches and flakes to appear on the skin. The rash often goes away for a while, but then it flares up again, often as a result of a trigger, such as stress. It is thought to happen when the immune system mistakenly starts producing skin cells too quickly. 

Psoriasis affects around 3 percent of people globally, and around 7.5 million people in the United States (U.S.). It affects men and women equally. It can begin at any age, but it is most common between the ages of 15 and 35 years, and again between 50 and 60 years. The average age is 28 years.


Plaque psoriasis is the most common type of psoriasis. Skins cells shed all the time, but in psoriasis, both dead and live cells collect on the skin's surface, because the replacement process is so fast.

The main symptoms of psoriasis are: red, flaky, crusty patches, covered with silvery scales that shed easily intense itching and burning. However, symptoms can differ, according to the type. Severity can range from mild to severe.

According to the National Psoriasis Foundation: mild psoriasis covers less than 3 percent of the body moderate psoriasis affects between 3 and 10 percent severe psoriasis covers over 10 percent of the body. Around 80 percent of people have mild psoriasis, and the other 20 percent have moderate to severe psoriasis.

Psoriasis can affect any part of the body, but it mostly appears as small patches on the elbows, knees, lower back, and scalp.