Psoriasis occurs when an overactive immune system speeds up skin growth. Normal skin cells grow and shed within a month. However, if you have psoriasis, skin cells can grow as quickly as 3–4 days.
Instead of shedding, new cells build up on the skin's surface, causing plaques and scales. Scaly patches of skin can happen anywhere on the body, but they commonly affect the elbows, knees, and scalp.
The exact cause of psoriasis is unknown. Psoriasis is considered an autoimmune condition, where the immune system mistakenly attacks healthy skin cells. Research suggests that genetics and environmental factors may also play a role.
Psoriasis is commonly associated with other health conditions, including:
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Type 2 diabetes
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Inflammatory bowel disease (IBD)
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Heart disease
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Psoriatic arthritis
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Anxiety and depression