Psoriasis causes red, scaly patches to appear on the skin. It can look like a rash, so you may worry that you could get it from someone else or pass it to others. But rest easy: It's not contagious. You cannot catch the disease by touching someone who has it. Though psoriasis symptoms show up on the skin, the condition is actually a problem with the immune system, called an autoimmune disease. It means the body’s defenses overreact or react at the wrong times, which affects the body inside and out. When people have psoriasis, their immune systems cause skin cells to grow much faster than normal. They pile up too quickly and form thick, scaly lesions. There are several different kinds of the disease, but the most common is plaque psoriasis. Lesions often appear on the knees, elbows, or scalp, although they can be anywhere on the body. These patches can feel swollen, itchy, and sore, and may crack and bleed. Other types of the condition may cause small red spots, pus-filled bumps, or red scaling patches all over. Scientists know that certain genes are linked to psoriasis. So if someone in your family has the condition, you may have the same genes and be more likely to get it yourself. Even when people have the right mix of genes, however, they also need something that triggers, or wakes up, their disease. It could be something physical, like a cut, scratch, bad sunburn, or an infection like strep throat. Stress, some medications, and cold weather (which can cause dry, cracked skin) are also common triggers. But being around someone else with psoriasis is not. Once something triggers psoriasis, it becomes a long-lasting condition. That means most people have it for the rest of their lives, although they may be able to control it with medication and other treatment. Before doctors knew what caused psoriasis, they often confused it with leprosy -- and people who had it were considered contagious. But now we know that you cannot catch the condition by brushing up against someone who has it. You also can't get it from kissing, having sex, or swimming in the same water. People get psoriasis because of their genes, not because of bad hygiene, their diet or lifestyle, or any other habits. They didn’t get it from someone else, and they cannot infect others. Even so, there’s a lot of stigma around the condition, which can be hard for people who have it. They might feel uncomfortable when people stare at their lesions or avoid touching them, and they may try to hide their outbreaks under long clothing. If you have psoriasis, you can help put an end to confusion and misunderstandings about the disease by talking openly with friends, family, and co-workers. And if you know people who have it, make sure they know that their condition doesn't affect your opinion of them or make you not want to be around them.