In most cases, diagnosis of psoriasis is fairly straightforward.
- Physical exam and medical history. Your doctor usually can diagnose psoriasis by taking your medical history and examining your skin, scalp and nails.
- Skin biopsy. Rarely, your doctor may take a small sample of skin (biopsy). He or she will likely first apply a local anesthetic. The sample is examined under a microscope to determine the exact type of psoriasis and to rule out other disorders.