context: Psoriasis turns your skin cells into type A overachievers: They grow about five times faster than normal skin cells. And your body can't keep up. The old ones pile up instead of sloughing off, making thick, flaky, itchy patches. Why do these cells go a little haywire? There's more going on under the surface of this skin disease. Researchers think something sets off your immune system. The exact reason is a mystery. But it's likely a combination of genetics and triggers. Little bits of your DNA, called genes, are instructions for your cells. They control things like your eye and hair color, if you can taste certain things, and other ways your body works. Some genes are only active at certain times. When you have psoriasis, the genes that control your immune system signals get mixed up. Instead of protecting your body from invaders as it's designed to do, it promotes inflammation and turns skin cells on overdrive. Scientists have found about 25 genes that are different in people with psoriasis. They think it takes more than one to cause the disease, and they're looking for the main ones. About 10 in every 100 people have genes that make them more likely to get psoriasis, but only two or three of them actually do. The disease often shows up or flares during puberty. Menopause can also trigger it. During pregnancy, your symptoms may get better or even go away. But after the baby's born, you might have a flare. Heavy drinkers have a higher risk, especially younger men. Alcohol can make treatments less effective, too. Lighting up can double your risk of getting psoriasis. If you also have relatives with the disease, you're nine times more likely to get it. And smoking makes it harder to get rid of symptoms. It's closely linked with a hard-to-treat type called pustular psoriasis, which affects the palms of your hands and the soles of your feet. Scientists think your immune system may respond to emotional and mental pressures the same way it does to physical problems like injuries and infections. Some treatments can make psoriasis worse. These include: Lithium, which treats bipolar disorder and other mental illnesses High blood pressure and heart medicines, including propranolol ( Inderal) and other beta-blockers, ACE inhibitors, and quinidine Antimalarial medicines, including chloroquine, hydroxychloroquine ( Plaquenil), and quinacrine Indomethacin ( Indocin), which treats inflammation Psoriasis usually is worse in the beginning stages of HIV infection, but then it gets better after you start certain treatments. Strep infections, in particular, are linked with guttate psoriasis, which looks like small, red drops. Kids will often have strep throat before their first flare. Earaches, bronchitis, tonsillitis, or a respiratory infection such as a cold, the flu, or skin problems. A little natural sunlight is good for most people with psoriasis. But for a few, the sun makes their condition worse. So can a bad sunburn, so protect your skin if you're going to be outside. A cut, scrape, bug bite, infection, or too much scratching can trigger the condition. People who are obese tend to get plaques in their skin creases and folds. Your psoriasis might be worse in the winter. Dry air, less natural sunlight, and cold temperatures can make symptoms worse. Keep your skin moist, and try a humidifier at home.