Unifying Concepts

Classification of Burn Injury

A burn is an injury to the skin or other organic tissue primarily caused by heat or due to radiation, radioactivity, electricity, friction or contact with chemicals. Skin injuries due to ultraviolet radiation, radioactivity, electricity or chemicals, as well as respiratory damage resulting from smoke inhalation, are also considered to be burns.

Classification of Burn Injury

Burns are classified as first-, second-, third-degree, or fourth-degree depending on how deeply and severely they penetrate the skin’s surface.

First-degree (superficial) burns. First-degree burns affect only the outer layer of skin, the epidermis. The burn site is red, painful, dry, and with no blisters. Mild sunburn is an example. Long-term tissue damage is rare and often consists of an increase or decrease in the skin color.

Second-degree (partial thickness) burns. Second-degree burns involve the epidermis and part of the lower layer of skin, the dermis. The burn site looks red, blistered, and may be swollen and painful.

Third-degree (full thickness) burns. Third-degree burns destroy the epidermis and dermis. They may go into the innermost layer of skin, the subcutaneous tissue. The burn site may look white or blackened and charred.

Fourth-degree burns. Fourth-degree burns go through both layers of the skin and underlying tissue as well as deeper tissue, possibly involving muscle and bone. There is no feeling in the area since the nerve endings are destroyed.


Depth Level of Injury Clinical Features Result/Treatment
Superficial (first degree) Epidermis Dry, red; blanches; painful Healing time 3–6 days, no scarring
Superficial partial thickness (superficial second degree) Papillary dermis Blisters; moist, red, weeping; blanches; severe pain to touch Cleaning; topical agent; sterile dressing; healing time 7–21 days; hypertrophic scar rare; return of full function
Deep partial thickness (deep second degree) Reticular dermis; most skin appendages destroyed Blisters; wet or waxy dry; reduced blanching: decreased pain sensation to touch, pain present to deep pressure Cleaning; topical agent; sterile dressing; possible surgical excision and grafting; scarring common if not surgically excised and grafted; earlier return of function with surgery
Full thickness (third degree) Epidermis and dermis; all skin appendages destroyed Waxy white to leathery dry and inelastic; does not blanch; absent pain sensation; pain present to deep pressure: pain present in surrounding areas of second-degree burn Treatment as for deep partial- thickness burns plus surgical excision and grafting at earliest possible time; scarring and functional limitation more common if not grafted
Fourth degree Involves fascia and muscle and/or bone Pain to deep pressure, in the area of burn; increased pain in surrounding areas of second- degree burn Healing requires surgical intervention


Other classification methods

  1. Type of burn: superficial (A), intermediate (AB), and “full thickness” or (B).
  2. Mechanisms of burns: classified as: flame, scalds, inflammables liquids; explosion, and others mechanisms.
  3. Burn surface: Defined as percentage of body according
  4. Garces´ Index: it is an index of prediction for mortality and is calculated according the following formula: 40 − age of patients + the percentage of burn body surfaces for 1 (burn type A), for 2 (AB) or for 3 (B).
    0–60 points: first degree (low risk).
    61–90: second degree (moderate risk).
    91–120: third degree (severe risk)



  1. Greenhalgh DG. Management of Burns. N Engl J Med. 2019 Jun 13;380(24):2349-2359. [Medline]
  2. Strobel AM, Fey R. Emergency Care of Pediatric Burns. Emerg Med Clin North Am. 2018 May;36(2):441-458. [Medline]
  3. Bittner EA, Shank E, Woodson L, Martyn JA. Acute and perioperative care of the burn-injured patient. Anesthesiology. 2015 Feb;122(2):448-64. [Medline]


Created Jun 21, 2019.

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