National Institute of
General Medical Sciences

Tissue damage caused by heat, chemicals, electricity, sunlight, or nuclear radiation. Burns are defined by how deep they are and how large an area they cover. Types of burns include:

• First degree: Damage only to the outer layer of skin (epidermis)
• Second degree: Damage to the outer layer and the layer beneath it (dermis)
• Third degree: Damage or complete destruction of both layers of skin
• Fourth degree: Extends into fat
• Fifth degree: Extends into muscle
• Sixth degree: Extends to bone