Critical Care Trauma Centre


Question of the Week: December 3, 1999

How are burns classified?

How are Burns Classified?
Partial Thickness 
(1st degree)
  • superficial burns are limited in depth to the first 2 or 3 of the 5 layers of the epidermis 
  • characterized by erythema, hyperemia, tenderness and pain
  • no vesicles or blisters
  • due to the shallow depth, regeneration of skin will occur within several days
Moderate Partial Thickness 
(2nd degree)
  • burns involve entire epidermis (blue zone) and upper third of dermis (mauve zone)
  • skin will usually appear red
  • injury to microvessels that perfuse the skin results in wet wounds with bullae and blisters
  • very painful; pain increases when exposed to air currents
  • will heal within 1 - 6 weeks with minimal scarring

Deep Partial Thickness 
(2nd degree)

  • burn includes the entire epidermus and deep into the dermis
  • impairment of blood supply often limits fluid leakage; blisters are not usually present and only a modest amount of plasma leakage appears on the wound
  • wound usually red with white appearance in center; blanches following assessment for capillary refill
  • dermal necrosis and surface protein turns gives burn surface a yellow appearance
  • will heal spontaneously by slow granulation, often leaving unstable epithelium, scarring and contractures
  • grafting is the desired treatment as it improves the quality of the healing (better cosmetic and functional healing) and reduces the opportunity for infection

  • can progress to full thickness injuries if infection develops
    Full Thickness Burn
    (3rd degree)
    • results in destruction of skin through all layers of epidermis and dermis, extending into subcutaneous fat and underlying tissue
    • subcutaneous layer contains hair follicles and sweat glands and is poorly vascularized; this is below the stratum germinativum layer (dark blue area) which is responsible for the generation of new skin cells
    • burn appears white, red or brown and is often charred and leathery in appearance 
    • skin is usually dry and insensitive to pin or palpation
    • if skin is broken, subcutaneous fat may be visible
    • associated with extensive fluid and electrolyte imbalances, altered thermoregulation, metabolic disturbances and infection

    • although small wounds will contract and eventually heal, larger wounds require grafting 
Diagram 1

blue area

Stratum Germinativum: 
dark blue area

mauve area

Subcutaneous Fat: 
yellow area

Burn Depths:
partial thickness (1)
moderate partial thickness (2)
deep partial thickness (3)
full thickness (4)

How is the "Percentage of Burned Area" Calculated?
Estimation of the size of the burn is done using the "rule of nines" shown in Diagram 2.  The corresponding area of burn is identified on the diagram, and the total percentage is calculated as the sum of the burned areas. 

The type or thickness of the burn can also be recorded on the diagram.  Many burns are mixed in nature, for example, the outer edges may be partial thickness, while areas of deep partial and full thickness burns may extend toward the center.  The appearance of the burn, along with the presence of blanching, blisters and pain helps to determine the extent of the injury. 

The percentage of burns may change as the tissue injury evolves and more extensive tissue damage becomes evident.  Infection can increase the severity of the burn over the course of the injury.

Diagram 2

Brenda Morgan.  (December 1, 1999)


Thelan, L., Urden, L., Lough, M., & Stacy, K. Critical Care Nursing: Diagnosis and Management. Mosby: Toronto.  pp. 1141-1170.

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