It is characterized by skin cells that multiply up to 10 times faster than normal, typically on the knees, elbows and scalp. As underlying cells reach the skin's surface and die, their sheer volume causes raised, white-scaled patches. Palmar or plantar psoriasis , which affects only the hands or feet, tends to be much more painful and often blisters and oozes. Though not contagious, psoriasis tends to run in families. Fair-skinned people aged 10 to 40 are particularly susceptible, especially those with a blood relative who suffers from the disorder.
Psoriasis is extremely rare among people with dark skin.
Outbreaks are triggered by the immune system and can affect other parts of the body, particularly the joints, in which case the condition is called psoriatic arthritis. Although psoriasis may be stressful and embarrassing, most outbreaks are relatively benign. With appropriate treatment, symptoms generally subside within weeks. Pitting, discoloring and thickening of the fingernails and toenails. If psoriasis develops on the nails, they may separate from underlying skin.