Slough is dead tissue on the surface of a wound. It’s one of three names for dead tissue in different states — slough, necrotic tissue, or eschar. All of these are devitalized tissue that may be removed during debridement.
You may see the same thing described without the word. Pressure sores can be covered in dead skin that is yellow, tan, green, or brown. That dead skin makes it hard to tell how deep the sore is, which makes the sore unstageable.
That is why slough matters rather than merely looking unpleasant. A wound covered in it can’t be measured properly, and measurement is how progress is tracked.
It also has to go. Dead tissue in a wound must be removed to help your wound heal. Ways to remove it include surgical debridement with sharp tools; a whirlpool bath; washing with a syringe; wet-to-dry dressings that pull dead tissue off as they are removed; and enzymes applied to dissolve it. When cleaning a stage II pressure sore, rinsing can remove loose, dead tissue.
Here’s what should be underneath. After debridement the wound may seem bigger and deeper, and the area will be red or pink in color and look like fresh meat. Wounds that are pale, purple, or black are less likely to heal.
One rule applies to all of this: you should never try to do this yourself.
Slough and eschar are not the same thing, and the difference matters because one of them is sometimes deliberately left in place. Wound Wizard has a separate article on eschar.