Dermatologists are doctors with added training that allows them to diagnose and treat diseases of the skin, hair, nails, and mucous membranes. Dermatologists treat skin cancers, moles, warts, fungal infections, psoriasis, acne, dry skin, contact dermatitis, and other skin conditions and perform cosmetic procedures. Dermatologists are also surgeons to prevent or provide early control of disease and improve how the skin looks.