A blister contains a fluid-filled sac within the upper layers of the skin.
The Contents of a Blister
Most blisters are filled with a clear fluid. This fluid is typically either serum or plasma, which are components of blood. However, depending on the cause, a blister may also contain lymph, blood, or pus.
- Serum and Plasma: These are the most common contents, forming a clear, watery fluid. They are components of blood responsible for carrying nutrients and other essential substances.
- Lymph: This is a clear fluid that is part of the body's immune system. Its presence in a blister may indicate an inflammatory response.
- Blood: Blood may be present in blisters caused by trauma, such as burns or severe friction. This would result in a blister that is reddish or bloody in appearance.
- Pus: If a blister is infected, it will likely contain pus, which is a thick, yellowish-white fluid containing white blood cells fighting off infection.
The type of fluid inside a blister depends largely on the cause of the blister. A simple friction blister will usually contain clear serum or plasma, while a burn blister might contain plasma and blood, and an infected blister will contain pus.
A blister is a small pocket of body fluid (lymph, serum, plasma, blood, or pus) within the upper layers of the skin, usually caused by forceful rubbing (friction), burning, freezing, chemical exposure or infection.