Blisters is the generic term for single or multiple skin eruptions, typically filled with clear fluid and on occasion, blood. Depending on size, they may be known as a vesicle or bulla. A vesicle is a fluid-filled, raised skin lesion up to 5 mm in diameter. A bulla is greater than 5 mm. Blisters form when the skin is damaged by physical trauma, high heat, cold or chemicals. The clear fluid that accumulates cushions the tissue underneath and thereby helps prevent further damage. That fluid also facilitates healing while the skin underneath begins to regenerate.
Physiologically, blisters form as an outpocketing of the skin, which subsequently becomes filled with fluid. Depending on the severity of the injury, the roof of the blister may compose one of the three distinct layers of the skin. The most superficial blister involves the outermost layer (stratum corneum) and is therefore classed a subcorneal blister. Other types are the suprabasal and subepidermal blisters.
Simple friction and other physical trauma are the most common causes of blister formation. Friction blisters usually crop up in the extremities, especially the feet and toes, because running or even walking causes repeated rubbing against the surfaces of ill-fitting footwear. In turn, blisters on your hands happen at work or while working around the house: pulling on ropes, typing, hand washing or using gardening tools. Surprisingly, moist skin is more prone to blisters than dry or thoroughly soaked skin.
Crushing the skin between two surfaces or simply pinching hard may lead to a blood blister. Instead of clear fluid, blood leaks into a space between the layers of the skin. This is caused by minute blood vessels rupturing because of the physical trauma.
The type of blister you are probably most familiar with is caused by high heat: accidentally touching an open flame, stove or cooking implement. When damage is slight and it is only a first-degree burn, it may be days before the blister forms. Experience a second-degree burn, however, and a blister forms almost immediately.
You can also get blisters from extreme cold. These are popularly known as frostbite.
Blisters can be caused by skin contact with a chemical such as makeup, detergent and solvents. Known as contact dermatitis, this occurs as tiny blisters when you have hypersensitive skin.
Blistering (Bullous) Diseases
Blisters appear in such conditions and diseases as viral herpes, spongiotic dermatitis, erythema multiforme, eczema, impetigo and chicken pox. There also exists a group of disorders where blister formation is the primary and most distinctive feature. Pemphigus is an example of a blistering disorder that is caused by autoantibodies that leads to the dissolution of intercellular attachments within the epidermis and mucous membranes. Although this is rare, delay in treatment is always fatal.
Blisters may be superficial and easily remedied, or they may be deep and life threatening. They are caused by various conditions, from physical trauma to autoimmune diseases. Whatever the cause or manifestation, it is always advisable to seek medical attention and treatment.