What is psoriasis? Psoriasis is a condition that appears on the skin as red, flakey, or crusty and scaly patches. Where these patches appear will depend on the individual, but often they show on knees, elbows, and scalp. This condition is a long-lasting ailment caused by the over-production of skin cells. Usually, skin cell turnover spans 3 to 4 weeks, but this skin condition hastens the process to 3 to 7 days. A variety of treatment plans are possible to help manage the condition. Consult with your doctor or visit a dermatologist for a diagnosis and a treatment plan.