Damage to skin or other tissues caused by agents such as fire, radiation, or corrosive chemicals. The severity of burns: first degree: skin is red in appearance, no blisters and sensation is intact (e.g., sunburn). second degree: partial thickness burn (thickness refers to the layers of the skin), blisters common, sensation is intact. third degree: full thickness burn, the skin is without sensation (anesthetic to touch), and dry with a leather-like or charred texture. The area of the body burned is usually expressed in percentages of the total body surface area that has sustained second and third degree burn. The following method can give a rough estimate of the area burn: adult: head 9%; anterior trunk 18%; posterior trunk 18%; each arm 9%; each leg 18%; genitals 1% child: the proportion of body areas changes with age, it is difficult to find a simple method to estimate the percentage of burned area