context: Psoriasis is a skin disease that affects about 7 million Americans. It comes in several forms, but plaque psoriasis is the most common. Plaques are raised red patches covered with a whitish buildup of dead skins cells called scale. They usually show up on your elbows, knees, scalp, and lower back, but you can have them anywhere. Plaques often itch or hurt. Doctors aren't sure why people get plaque psoriasis. It's considered an autoimmune disease. That means your immune system attacks healthy cells as if it's fighting an infection. This causes new skin cells to grow much faster than normal, and they build up in thick patches. Whether you get plaque psoriasis depends on your genes and your health history: Heredity: Psoriasis seems to run in families. About 10% of people are born with genes that make them likely to get psoriasis. But only about 3% of people get the disease. Triggers: Something has to happen to start your immune system's reaction. Sometimes it's an injury to your skin or a bad sunburn. It could be a certain medicine, like lithium or malaria drugs. An infection, particularly strep, can bring on psoriasis. So can high levels of stress. Psoriasis isn't contagious. It can't be spread by touch or other close contact. People with psoriasis tend to have other conditions that cause inflammation, like Crohn's disease, diabetes, metabolic syndrome, fatty liver disease, and obesity. If you have it, you may be more likely to get heart disease, depression, and a kind of eye disease called uveitis. You also have as much as a 1-in-3 chance of getting psoriatic arthritis, which causes joint pain, stiffness, and swelling, and joint deformity. A dermatologist (skin doctor) can usually tell if you have plaque psoriasis just by talking with you about your medical history and looking at your skin. In some cases, he may need to do a biopsy to know for sure. He'll take a tiny sample of your skin and look at the cells under a microscope. Psoriasis can't be cured. You'll probably go through cycles where the rash looks better, then flares up again. The goal of treatment is fewer, less severe flare-ups. You may get medicine to put on your skin or you may take pills, or your doctor may recommend a combination of those. Treatment options include: Topical medications: If you have only a few plaques, your doctor will probably try a prescription cream first. You put these directly on your skin. They either help with inflammation or slow the growth of skin cells. Examples include corticosteroids, vitamin D, vitamin A, and anthralin. You can also try over-the-counter topical medicines. Both salicylic acid and coal tar are approved to treat psoriasis. Other ingredients may soothe itch and remove scale, including aloe vera, jojoba, zinc pyrithione, and capsaicin. Topical emollients that you put on after a shower or bath can help keep your skin moist. Light therapy: If the rash is more widespread, your doctor may treat it with ultraviolet light. This is done at her office or with a special box you can keep at home. You may also get relief by going out in the sun, but this can raise your risk of skin cancer. Watch how long you spend outside, and cover up or put sunscreen on places where you don't have plaques. Systemic drugs: If you have a severe case of plaque psoriasis, you may need medicines that work throughout your body. They calm your immune system or make your skin cells grow more slowly. But they can cause serious side effects, like depression, aggressive thoughts, liver problems, or a higher risk of skin cancer. You take systemic drugs like acitretin, cyclosporine, and methotrexate by pill, or your doctor will give you a shot. Biologic drugs: Another kind of systemic drug also targets your immune system. Biologic drugs used to treat psoriasis include adalimumab ( Humira), brodalumab ( Siliq), etanercept( Enbrel),guselkumab ( Tremfya), infliximab ( Remicade), ixekizumab ( Taltz), risankisumab-rzaa ( SKYRIZI)),secukinumab ( Cosentyx), and ustekinumab ( Stelara). They're given either by a shot or through a vein in your arm. They affect a specific type of immune cell or keep certain proteins from causing inflammation. But these drugs can make it harder for you to fight an infection. Most people who get plaque psoriasis have it for the rest of their lives. You can do a few things to deal with it better: Avoid triggers: Things like stress and smoking don't cause psoriasis. But they can make it worse. Try to figure out what triggers your flare-ups. You may be affected by: Alcohol Allergies Cold, dry weather Hormones Watch your diet : There's no proof that specific foods make a difference with psoriasis. But losing weight may keep your symptoms at bay, so it makes sense to eat healthfully. And a diet low in fatty meat and dairy products and high in fish and colorful fruits and vegetables may help with inflammation. Take care of your skin: A good moisturizer can keep plaques soft and make you less itchy. A bath with colloidal oatmeal or Epsom salts can also soothe your skin. Get support: Plaque psoriasis can take an emotional toll. You may feel self-conscious about the way it looks or overwhelmed by what it takes to manage it. Many people with psoriasis become depressed. If you think you need some help, talk with your doctor about therapy or medication. It also helps to talk with people who understand what you're going through and can offer strategies for coping. Work with your doctor: Talk with him about how you're doing and any changes to your condition. You may need to change your treatment over time. Don't suddenly stop using a psoriasis drug or you could cause a more serious illness. Be aware of symptoms that could signal psoriatic arthritis, like joint pain.