Unlike instantaneous burns from touching a heat source, sunburn inflammation and redness usually start about four hours after exposure. Maximum redness generally occurs within 12 to 24 hours, and the painful, burning sensation occurs from 6 to 48 hours after exposure. After a couple days, the outer layers of skin may peel away. Peeling is actually the body’s way of healing itself by shedding the top layer of damaged epidermis.
Severe sunburns can cause chills, fever, nausea, and blistering in various degrees. In cases in which people are stranded without shelter, extremely severe sunburns can cause what is known as sun poisoning. Sun poisoning may be life threatening. It results in severe blistering, a lack of fluids, an imbalance in important chemicals, and it may even lead to deadly infections.
Follow this link to watch a really good animation video explaining sunburn, from Skincancer.org
The Skin Cancer Foundation – Sunburn.