Sunburn is an acute inflammatory skin reaction caused by overexposure to ultraviolet (UV) radiation from the sun or artificial sources like tanning beds, resulting in damage to the epidermis and sometimes deeper layers. It typically appears within a few hours of exposure as red, warm, tender, or painful skin that may swell, develop blisters (in moderate to severe cases), and feel tight or itchy. Common affected areas include the face, shoulders, arms, back, and legs, often with clear lines showing where clothing or sunscreen protected the skin. Peeling usually begins 3–8 days later as the damaged skin sheds. Severity ranges from mild (slight redness and discomfort) to severe (intense pain, widespread blistering, fever, chills, headache, or nausea indicating systemic involvement or heat exhaustion). Repeated or severe sunburns increase the long-term risk of premature skin aging, pigmentation changes, and skin cancers.