In an extensive burn, loss of a large amount of fluid from abnormally leaky blood vessels can cause shock. In shock, blood pressure decreases so much that too little blood flows to the brain and other vital organs. Most electrical burns also severely damage the tissues under the skin. These burns vary in size and depth and may affect an area much larger than that indicated by the area of injured skin. Large electrical shocks can paralyze breathing and disturb heart rhythm, causing dangerously irregular heartbeats.
Chemical burns can cause tissue death that can slowly spread for hours after the burn.
The severity of a burn depends on the amount of tissue affected and the depth of the injury, which is described as first, second, or third degree. First-degree burns are the least severe. The burned skin becomes red, painful, very sensitive to the touch, and moist or swollen. Second-degree burns cause deeper damage. The skin blisters.