A dermatologist's concerns include CYSTS, rashes, and acnes. CYSTS are closed sacs filled with fluid, gas, or other material that can form under the skin. Rashes are areas of irritated or swollen skin that can be caused by a variety of factors, such as allergies, infections, and environmental irritants. Acne is a common skin condition characterized by pimples, blackheads, and whiteheads. All of these conditions can cause discomfort and embarrassment, and a dermatologist can help diagnose and treat them.