Psoriasis is a chronic skin condition that affects about three percent of the population. Psoriasis causes your body to make skin cells too quickly, and they pile up on the surface of your skin. The buildup results in thick, red skin that may be covered with silvery scales. Psoriasis can occur anywhere on your body but is most common on the knees, elbows and scalp. It is not contagious.

Psoriasis is caused by an overreaction of your immune system. White blood cells called T cells normally help you fight off viruses and bacteria. But, if you have psoriasis, your T cells attack normal skin cells and cause irritation and swelling, called inflammation. The attack also causes your body to produce skin cells more quickly.

Why this happens is not clear. It may be caused by inherited genes that are triggered at some point. Triggers may start psoriasis symptoms or start the attacks of psoriasis that follow. Triggers for psoriasis may include:


Skin injury or sunburn



Exposure to cold



Certain medications, such as lithium, beta blockers and medications used to treat malaria

Psoriasis usually starts between ages 15 and 35. It can range from mild symptoms that affect a small area of skin to severe symptoms that affect a large area. For most people, psoriasis comes and goes. You may have a flare-up of symptoms that last for weeks or months and then get better. About 10‒30 percent of people with psoriasis also develop a type of joint swelling and pain called psoriatic arthritis.

There are many ways to treat psoriasis and psoriatic arthritis. Work with your doctor to find the treatment that's best for you.