Even if you don't have psoriasis and don't know anyone with this skin condition, it's helpful to be aware of the myths and facts, especially on World Psoriasis Day.

Between 5.8 million and 7.5 million people live with the skin disease psoriasis, yet almost half with moderate to severe cases are not getting treatment and others are receiving out-of-date treatment.

Health.com: How to Find a Psoriasis Treatment That Works

Why is effective treatment for psoriasis such a challege? Because the condition is still widely misunderstood—people who live with it can be subject to prejudice and discrimination—and treatments have not been very good until now.

Health.com: Test Your Psoriasis IQ

There are five types of psoriasis: plaque (the most common form), guttate, inverse, pustular, and erythrodermic. Psoriasis can appear anywhere on the body and up to 30% of people with psoriasis will develop psoriatic arthritis, a painful condition in which joints are inflamed and stiff.

Health.com: How Managing Stress May Help Your Psoriasis

Psoriasis is largely an inherited condition, but it involves multiple genes and possibly some environmental factors to bring the disease on. Common triggers include stress; skin trauma, such as sunburn or wounds; some medications, including antimalarial drugs; and, in the case of guttate psoriasis, strep infection.

Health.com: Can A Healthy Diet Help Psoriasis?

Though many patients find that certain diets help clear their skin, or that certain foods aggravate it, no studies have established a definitive link between nutrition and psoriasis, says Neil Korman, MD, clinical director of the Murdough Family Center for Psoriasis in Cleveland Heights, Ohio. “There’s no ‘Psoriasis Diet,’ but people with psoriasis should try to eat a healthy diet,” he says. “We do know that people who are obese are at increased risk for psoriasis, and that losing weight may help improve your psoriasis.”

Health.com: Psoriasis Skin-Care Product Guide

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