The exact cause of psoriasis, a long-lasting skin condition, is still unknown. But researchers have identified several things that may trigger the disease. Once you have psoriasis, these same factors may cause new flare-ups. Many people with psoriasis have close relatives with the disease. Genes are thought to play a key role in determining who's at risk. Researchers believe that at least 10 percent of Americans carry one or more genes linked to psoriasis. Yet only about 3 percent develop the disease. This suggests that it's a combination of genetic and other factors that causes psoriasis to appear. Unlike your genes, the risk factors below are wholly or partly under your control. That’s good news, because it means you can take steps now to reduce your risk for psoriasis in the future. Stress A high level of stress seems to set off psoriasis in some people. Once the disease is active, changes in the skin can cause physical discomfort and emotional distress. And that, in turn, can lead to even more stress, setting a vicious cycle in motion. What you can do: Break the cycle by learning to manage stress effectively. Exercise, support groups, and relaxation techniques (such as meditation or yoga) can all help. Infections Infections that put your immune system on guard can also play a part in your psoriasis. For example, a form of the disease called guttate psoriasis is often triggered by strep throat. What you can do: Protect your health by washing your hands often and getting plenty of rest. If you develop symptoms of guttate psoriasis—small, drop-shaped spots on your chest, stomach, limbs, or scalp—ask your doctor whether you need a strep test. A strep infection can sometimes cause this type of rash even when you don’t have a sore throat. Obesity A 2007 study in the Archives of Internal Medicine looked at the link between obesity and psoriasis. Researchers followed 78,626 women for 14 years. They found that weight gain was a strong risk factor for developing psoriasis. What you can do: If you’re overweight, slimming down may lower your odds of getting psoriasis. If you already have psoriasis, shedding extra pounds may reduce the severity of symptoms and boost the effectiveness of treatment. Smoking Research points to smoking as another possible risk factor for developing psoriasis. For those who already have psoriasis, smoking may worsen the disease. The link is especially strong in localized pustular psoriasis, which causes blisters of noninfectious pus, usually on the palms of your hands and soles of your feet. What you can do: If you don't smoke, this is one more good reason not to start. If you're already a smoker, ask your doctor how to quit. Or call 800-QUITNOW (784-8669) for a quit-smoking hotline in your state. Alcohol Studies suggest that heavy alcohol drinking may trigger or worsen psoriasis. It may also make treatment for psoriasis less effective. What you can do: If you drink alcohol, do so in moderation. That means no more than two drinks on any single day for men and one drink for women. But if you're taking methotrexate, a medication prescribed for severe psoriasis, don't drink at all. Mixing this medication and alcohol can cause serious side effects.