The seriousness of a burn depends on where it is on the body, how extensive it is, the physical condition and age of the victim, how hot the agent which caused it was and how long the exposure to that agent was. Burns are thus normally classified into three types:

First degree burns.
These affect the superficial layer of the skin and while they may be mildly painful, they are not serious. The skin reddens, and goes dry and inflamed.
Causes. Too much exposure to the sun or brief exposure to hot objects: iron, liquids...
What to do? Cool the affected area down with abundant cold running water and treat with anti-inflammatories, and ointment or cream for burns.

Second degree burns.
These affect the superficial and underlying skin layers. They cause intense pain, the skin may blister and the affected area becomes inflamed.
Causes. Too much exposure to the sun or a brief exposure to hot objects: iron, liquids...
What to do? You should cover blisters with sterile dressings soaked in a physiological serum (saline solution) and never burst them, in order to avoid infections and scarring. Neither should you apply ice to the wound, nor any grease, cream or oil. Give the patient plenty to drink and, if necessary, administer some sort of painkiller or sedative. If the burn is in a delicate area like the genitals, neck, throat or face, or affects a large area of skin, a doctor should be brought in immediately.

Third degree burns.
Also known as full thickness burns, these damage all the layers of the skin, affecting the underlying tissue, the blood vessels, tendons, nerves, muscles and even the bone. The skin becomes dry and thickens but there is no pain due to the destruction of nerve endings.
Causes. They are caused by prolonged contact with hot, caustic or electrical objects.
What to do? The patient needs to get to a hospital as soon as possible. You should not try to remove any clothing stuck to the body, nor should you put anything on the burn apart from some sterile dressings soaked in physiological serum to prevent infection. Give the victim copious liquids, preferably salt water (four teaspoons of salt to a litre of water).

Frequent causes of burns
- Physical Agents. Irons and stoves. Boiling liquids, such as water or oil. And exposure to ultra low temperatures too.
- Chemical Agents. Gasoline and petroleum derivatives. Hydrochloric and sulphuric acid. Caustic soda, lime and carbide.
- Electricity. Electric shocks of various voltages, sun rays, X-rays and infrared rays.