To diagnose psoriasis, a dermatologist:

• Examines a patient’s skin, nails, and scalp for signs of psoriasis.
• Asks whether family members have psoriasis.
• Learns about what has been happening in the patient’s life. A dermatologist may want to know whether a patient has been under a lot of stress, had a recent illness, or just started taking a medicine.

Sometimes a dermatologist also removes a bit of skin. A dermatologist may call this confirming the diagnosis. By looking at the removed skin under a microscope, one can confirm whether a person has psoriasis.