If you've been caught in the sun without sunscreen, you would normally expect to bum. A useful trick to prevent burning is to take acetylsalicylic acid (aspirin) before the bum appears. The first phase of a bum is largely the result of the ultraviolet light's interaction with the skin, causing the release of chemical prostaglandins. Aspirin is an antiprostaglandin, therefore it can effectively block the action of the prostaglandins in the skin if it is taken early enough. Two adult aspirin 3 times daily for 2 days may be helpful, if your digestive system can stand it.