Scalp psoriasis is a condition of the scalp in which the outer layer of skin cells reproduce faster than normal and the skin develops a build-up of dry, dead skin cells. These cells form thick, silvery scales and can be accompanied by itching, soreness, and burning. Sometimes, the skin may become so dry as to crack and bleed. While this condition can occur at any age, according to the Mayo Clinic, diagnosis commonly occurs between the ages of 15 and 35. Fortunately the disease is not contagious and many doctors believe it to be inherited and triggered by factors including stress, infection, or skin injury.
Unfortunately, for those suffering with psoriasis, the condition can be a long-term problem which may come and go and vary in severity from a mild to disabling. The upside is that psoriasis can most often be controlled. The condition presents itself very similarly to seborrheic dermatitis (sometimes called cradle cap) and the treatment options are similar as well.
Doctors may use a variety of treatments, including topical corticosteroid creams, synthetic vitamin D3 (not the same as over-the-counter supplements), topical retinoid, salicylic acid creams, moisturizers, and coal tar. Other treatments include light therapy and oral medications or injections. Your doctor can prescribe treatment options based on the severity of your condition.
While I certainly recommend seeing your doctor before trying any type of self-treatment option, I have known people who have had great success with tar shampoos such as MG217 Medicated Tar Shampoo. Again, you'll really want to see your doctor for a proper diagnosis and treatment.
For more information on Psoriasis and how it is treated, I recommend visiting the Psoriasis Section of About.com.