A burn destroys skin cells, and the deeper the damage, the less the skin can repair itself. Both the depth and the area of the burn decide how serious it is.
Depth
Superficial burns affect only the epidermis. Partial-thickness burns reach into the dermis, and full-thickness burns destroy both layers, including the nerve endings.
Size
Burn size is given as a percent of total body surface area (TBSA). The rule of nines gives each arm about 9 percent and each leg about 18 percent in adults, and the patient's palm with fingers is about 1 percent.
Whole-body effects
Large burns let fluid leak out of the vessels, which can cause shock. The lost barrier also means heat loss, hypothermia and a high risk of infection.
Airway burns
Burns in a closed space, soot around the mouth or a hoarse voice suggest the airway is injured. Swelling can block the airway within hours.
| Depth | Layers involved | What you see |
|---|---|---|
| Superficial | Epidermis | Red, dry, painful, no blisters |
| Superficial partial-thickness | Epidermis and upper dermis | Blisters, moist, pink, very painful |
| Deep partial-thickness | Deeper dermis | Blotchy red or white, less painful |
| Full-thickness | Epidermis, dermis and beyond | White, brown or leathery, little or no pain |
At the bedside
Cool the burn with running water for 20 minutes, then estimate depth and TBSA, counting only partial- and full-thickness areas. The TBSA guides fluid replacement and the decision to send the patient to a burn center.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).