What it is:
Sunburn, also called erythema, is one of the most obvious signs of UV exposure and skin damage. Often marked by redness and peeling (usually after a few days), sunburn is a form of short-term skin damage.
Why it happens:
When UV rays reach your skin, they damage cells in the epidermis. In response, your immune system increases blood flow to the affected areas. The increased blood flow is what gives sunburn its characteristic redness and makes the skin feel warm to the touch. At the same time, the damaged skin cells release chemicals that send messages through the body until they are translated as a painful burning sensation by the brain.
White blood cells, which help protect you from infection and disease, attack and remove the damaged skin cells. It is this process of removing damaged cells that can cause sunburned skin to itch and peel.
The earliest signs of sunburn are skin that looks flushed, is tender or painful, or gives off more heat than normal. Unfortunately, if your skin tone is medium to dark you may not notice any obvious physical signs until several hours later. It can take 6 - 48 hours for the full effects of sunburn to appear.
The American Academy of Dermatology (AAD) recommends treating mild sunburn with cool baths, over-the-counter hydrocortisone creams, and aspirin to ease pain and swelling.
Severe sunburn should be treated as a medical emergency and examined by a doctor right away. Severe sunburn is often characterized by a large area of red, blistered skin with a headache, fever, or chills.
The Bottom Line:
Sunburn can be a very painful effect of UV exposure. Studies have shown a link between severe sunburn and melanoma, the deadliest form of skin cancer. Pay careful attention to protecting yourself from UV rays.