| Depth | Cause | Surface Colour | Pain Sensation |
|---|---|---|---|
| Superficial | Sun, flash, minor scald | Dry, minor blisters, erythema, brisk capillary return | Painful |
| Partial thickness / superficial dermal | Scald | Moist, reddened with broken blisters, brisk capillary return | Painful |
| Partial thickness / deep dermal | Scald, minor flame contact | Moist white slough, red mottled, sluggish capillary return | Painless |
| Full Thickness | Flame, severe scald or flame contact | Dry, charred whitish. Absent capillary return | Painless |
Minor / Superficial
These burns affect only the epidermis. They heal in a few days with little trouble and minimal discomfort and require little more than a first aid dressing.
Superficial Partial Thickness
Involves the entire epidermis and no more than the upper third of dermis. Rapid re-epithelialisation occurs in 1-2 weeks. Due to the presence of a large number of remaining epidermal cells and a good blood supply there is normally a small zone of injury or stasis beneath the burn eschar.
Mid Dermal Partial Thickness
Thermal destruction of the epidermis occurs to the level of the basement membrane plus the middle third of dermis. Re-epithelialisation is much slower (2-4 weeks) due to fewer remaining epidermal cells and less blood.
Deep Dermal Partial Thickness
Involves the entire epidermis and at least two thirds of the dermis leaving very few dermal and epidermal cells to regenerate. Spontaneous healing is very slow and may take over four weeks. Surgical debridement is needed to remove dead tissue. Scarring can be severe if not skin grafted and there is a high risk of infection. After healing, the function of a re-epithelialised deep partial thickness burn is poor due to fragility of the epidermis and the rigidity of the collagen laden scar tissue within the dermis.
Full Thickness
A full thickness burn occurs with destruction of the entire epidermis and dermis, leaving no residual epidermal cells to repopulate. This wound will not, therefore, spontaneously re-epithelialise and the area of the wound not closed by wound contraction will require skin grafting. Direct exposure to flame or hot liquids is the usual cause of full thickness burns. The burn wound is also painless due to the destruction of the pain receptor system.
Donor Sites
It is common to apply a skin graft to deeper burns, usually taken from undamaged areas of the patient. These donor sites are acute wounds which require appropriate wound management. They generally heal without complication though they can be painful, have high levels of exudate and infection remains a risk.