Burns may be classified according to degree or according to skin thickness.

Classification by degree:

• First degree burns: painful, tender, reddened skin without blisters
• Second degree burns: painful, tender, redness skin with blisters
• Third degree burns: painless, charred skin that becomes white or dark
• Fourth degree burns: burns involving muscle, bone or other structures beneath the skin

Classification by thickness:

• Partial-thickness burns:
• Injury limited to the outer layers of the skin
• Full-thickness burns:
• Injury to all the layers of the skin