Burns can be caused by fire, the sun, chemicals, heated objects or fluids, and electricity. They can be minor problems or life-threatening emergencies. Distinguishing a minor burn from a more serious burn involves determining the degree of damage to the tissues of the body. If you are not sure how serious the burn is, seek emergency medical help. First-degree burns are those in which only the outer layer of skin is burned. The skin is usually red and some swelling (肿大) and pain may occur. Unless the burn involves large portions of the body, it can be treated at home. Second-d