Burn injuries are common, ranging from minor discomfort to serious medical emergencies. When skin is damaged by heat, blisters often form as a natural defense. These fluid-filled pockets serve as a protective layer, helping the body heal underlying tissue. Understanding their nature is important for proper care and to prevent complications.
The Composition of Blister Fluid
The fluid found within a burn blister is primarily serum, the clear, liquid component of blood plasma. This serum leaks from small blood vessels damaged by the burn injury. The fluid contains water, electrolytes, and various proteins, including albumin and immunoglobulins (antibodies involved in the immune response).
The blister fluid also contains immune cells, growth factors, and cytokines—signaling molecules that help regulate healing processes. It provides a sterile, nutrient-rich environment that aids in the regeneration of new skin cells and acts as a natural barrier against infection. The fluid is not pus; pus typically indicates an infection and has a different appearance and composition.
How Burn Blisters Develop
Burn blisters form from the body’s response to heat damage. When skin cells and blood vessels are injured by high temperatures, an inflammatory response is triggered. This response leads to increased permeability of blood vessels, allowing fluid to leak into the damaged tissue.
The accumulation of this fluid causes the outer skin layer, the epidermis, to separate from the dermis beneath it, creating the characteristic fluid-filled sac. Blisters are most commonly associated with superficial partial-thickness (second-degree) burns, where both the epidermis and a portion of the dermis are affected. Full-thickness (third-degree) burns, which involve deeper tissue layers and often destroy nerve endings, typically do not blister due to extensive damage.
Caring for Burn Blisters
Avoid popping or draining a burn blister. Popping removes its natural protective barrier, increasing infection risk and potentially prolonging healing. If a blister breaks on its own, gently clean the area with mild soap and water. After cleaning, cover the area with a loose, sterile non-stick dressing to protect the healing skin.
Prompt medical attention is necessary for certain burn blisters. Seek professional evaluation if a blister is large, such as bigger than a quarter or covering a significant body area. Blisters on critical areas like the face, hands, feet, genitals, or major joints require medical assessment.
Signs of infection, including increased redness, spreading pain, pus, a foul smell, or fever, indicate a need for medical intervention. Burns caused by chemicals or electricity, or full-thickness burns that appear white, leathery, or charred and may be painless, require immediate medical care. Infants, young children, older adults, and individuals with compromised immune systems should seek medical attention for burns, even if they seem minor.