Burns are injuries primarily to the skin and underlying tissue. The skin is the largest organ in the body and it regulates the body's temperature. It also prevents the evaporation of bodily fluids and acts as a barrier against infection.
Skin damage resulting from burns can be minor or can present a life-threatening emergency, depending on the heat's intensity, the total area of tissues burned, and the length of exposure to the skin.
Burns tend to be caused by a variety of environmental factors:
Burns are generally classified according to the depth and extent of injury: first-degree, second-degree, or third-degree burns. There are three layers of skin. Burn depth is dependent on which layer of skin has been damaged. Symptoms range depending on the depth of damage.
First-degree burns involve the outermost layer of the skin, called the epidermis. Redness, tenderness or pain, and swelling usually describe these burns. There's usually no blistering. Complete recovery usually occurs within a week, often with peeling and sometimes with temporary, mild changes in skin tone. First-degree burns often occur after over-exposure to UV rays of the sun, or after coming in contact with a hot object.
Second-degree burns involve damage to the second layer of skin, called the dermis. These very painful burns look pink, moist and soft. Blisters usually appear and fluid might ooze from the skin. Depending on the damage to the dermis, these burns may take anywhere from 2 to 6 weeks to heal. Scarring may result. Such burns often result from severe UV exposure and scalds.
Third-degree burns involve damage to the epidermis, the dermis, and the hypodermis, the third layer of skin. As a result, the full thickness of the skin is damaged. Fat, nerves, muscles, and bones may be affected. Damage of this sort causes the skin to appear a filmy white. The area isn't generally painful because nerve endings have been damaged. Since a large amount of tissue may be destroyed, healing is very slow and considerable scarring results. Later on, contractures (permanent tightening of tissue that prevents normal movement) can occur due to the deep scarring and occasionally tissue may have to be cut or "released" to relieve underlying pressure. Deep burns may result from contact with fires, electricity, or corrosive chemicals.
Inhalational burns can lead to airway swelling and inability to breathe; people with these injuries must be brought to a hospital as soon as possible, even if they initially do not have breathing difficulties.