Dermatologists diagnose skin problems, from mild ones (e.g. sunburn) to severe ones (e.g. skin cancer). They conduct screenings and skin evaluations, and analyze the patients' medical history to determine appropriate treatments. A dermatologist is a medical doctor who specializes in conditions that affect the skin, hair, and nails. Whether it's rashes, wrinkles, psoriasis, or melanoma, no one understands your skin, hair, and nails better than a board-certified dermatologist.