Burns is one of the Afflictions that can affect the player in The Long Dark. It is caused by stepping on a hot object such as a burning campfire.
The screen will flash red when this happens, and the player can treat this in the First Aid menu.
Condition will be slightly decreased if the player picks up a burn. But far more dangerously, the player's maximum condition will be set at 75%, and will not recover past this point, until the burns are treated (although if Condition was higher, it will remain higher unless it's reduced by other sources).
To treat a burn, the player must use a Bandage and either two Painkillers or a cup of Rose Hip Tea at which point, the burns will be immediately gone. An Old Man's Beard Wound Dressing will not work on a burn. Burns will go away on their own eventually, but there is no rest prompt or set amount of elapsed time until it happens.