Psoriasis is thought to be an immune system problem that causes skin cells to grow faster than usual. In the most common type of psoriasis, known as plaque psoriasis, this rapid turnover of cells results in dry, scaly patches.
The cause of psoriasis isn't fully understood. It's thought to be an immune system problem where infection-fighting cells attack healthy skin cells by mistake. Researchers believe that both genetics and environmental factors play a role. The condition is not contagious.
Psoriasis triggers:
Many people who are predisposed to psoriasis may be free of symptoms for years until the disease is triggered by some environmental factor. Common psoriasis triggers include:
• Infections, such as strep throat or skin infections
• Weather, especially cold, dry conditions
• Injury to the skin, such as a cut or scrape, a bug bite, or a severe sunburn
• Smoking and exposure to secondhand smoke
• Heavy alcohol consumption
• Certain medications — including lithium, high blood pressure drugs and antimalarial drugs
• Rapid withdrawal of oral or injected corticosteroids
Courtesy: Mayo Clinic