Psoriasis

Thick, red patches of skin covered with white or silvery scales are signs of psoriasis. Doctors know how psoriasis works -- your immune system triggers new skin cells to grow too quickly -- but they don't know what causes it. The patches typically show up on your scalp, elbows, knees, and lower back. They can heal and come back throughout your life. Treatments include creams and ointments for your skin, light therapy, and medications taken by mouth, injection, or IV.