Blisters
Blisters are small fluid-filled sacs of skin that develop as a response to external injury, infectious diseases, or autoimmune disorders.
Symptoms and Causes
Blisters are fluid-filled elevations that form in the superficial layer of the skin as a result of friction, heat, or skin diseases. They most commonly appear on the hands and feet, although they may develop on other parts of the body.
The fluid inside blisters is a mixture of blood plasma, water, and proteins produced by the body as a protective response. It is usually clear or light yellow in color, but it becomes darker when blood is present because the lesion has reached the capillaries beneath the skin. This serous fluid acts as a natural dressing that protects nerve endings and damaged tissue against infection, impacts, or friction.
Although they are uncomfortable, blisters are usually benign and disappear without the need for medical treatment. However, when they appear in unusual locations or without an apparent cause, it is advisable to consult a specialist for proper evaluation.
Symptoms
The characteristic symptoms of blisters are:
- Raised areas of skin filled with fluid that may appear individually or in clusters.
- Vesicles: small lesions with a diameter of less than 5 millimeters.
- Bullae: larger lesions with a diameter greater than 5 millimeters.
- Burning sensation.
- Itching.
- Tenderness to touch.
- Occasionally pain, especially when pressure is applied to the blister.
Infected blisters present the following signs:
- Redness of the skin covering and surrounding the lesion.
- Sharp pain.
- Pus discharge (a thick yellow or green fluid containing serum, leukocytes, and dead cells).
- Warmth in the affected area.
- Fever.
- Fatigue.
- Generalized body pain.
Causes
Blisters may develop due to a wide variety of causes:
- Skin blisters: may occur anywhere on the body.
- Burns: develop in second-degree burns caused by exposure to fire, very hot materials, chemicals, electricity, or solar radiation. In third-degree burns, blisters are part of the healing process.
- Insect bites: trigger an inflammatory reaction that resolves quickly in the absence of allergy.
- Skin diseases:
- Bullous impetigo: bacterial infection caused by Staphylococcus aureus.
- Pemphigus vulgaris: autoimmune disorder characterized by painful blisters on the skin and mucous membranes.
- Bullous pemphigoid: autoimmune disease that causes pus-filled bullae.
- Dermatitis herpetiformis: associated with celiac disease and causes blisters and itching.
- Epidermolysis bullosa: genetic disorder in which the skin is extremely fragile and more prone to blistering.
- Herpes zoster: reactivation of varicella-zoster virus infection affecting peripheral nerves and the skin, causing painful band-like blisters.
- Chickenpox: infection caused by the varicella-zoster virus characterized by a rash that, after the initial inflammation, develops into blisters. Crusts appear once the lesions dry.
- Hand, foot, and mouth viral exanthem: commonly known as hand, foot, and mouth disease, it is an infection caused by the Coxsackie virus that is common in children. It presents with fever, mouth sores, and blisters on the hands and feet.
- Foot blisters:
- Friction or repetitive rubbing against rough surfaces when walking barefoot or when wearing poorly fitting shoes.
- Sweating: moisture softens the skin, increasing friction.
- Excessive heat: walking barefoot on very hot surfaces.
- Infections: bacteria or fungi penetrating the superficial layer of the skin may cause blisters.
- Poor circulation: inadequate blood flow causes tissue damage that results in inflammation and wounds.
- Hand blisters:
- Constant friction from using tools or sports equipment without protection.
- Dyshidrosis: chronic dermatitis characterized by blisters resulting from stress, heat, or excessive sweating.
- Mouth blisters:
- Aphthous ulcers: ulcers that appear on the lips or tongue due to a weakened immune system, hormonal changes, stress, or trauma.
- Fever blister: herpes labialis caused by the herpes simplex virus.
- Genital blisters: are usually a sign of genital herpes, a sexually transmitted infection. They commonly appear on the penis, glans penis, vulva, or anus.
Risk Factors
Factors that increase the risk of developing blisters include:
- Wearing inappropriate footwear: new, stiff, overly loose, or very tight shoes exert pressure or cause friction on the foot.
- Not wearing socks.
- Excessive friction of objects against the skin.
- Very high temperatures.
- Exposure to sunlight, direct heat, or chemical agents.
- Allergies.
- Environments with large numbers of insects.
- Diseases associated with blister formation.
Complications
Although uncommon, blisters may cause serious complications:
- Wound infection: if the blister ruptures, bacteria can more easily access the injured area.
- Cellulitis: bacteria spread to the skin surrounding the lesion, causing redness and inflammation. Fever may also occur.
- Scarring: if the skin is removed prematurely, visible and long-lasting scars may remain.
- Dehydration: some blistering disorders may cause significant fluid loss.
What doctor treats blisters?
Blisters are treated by a variety of medical specialties depending on their nature and location. In most cases, these include Medical-surgical dermatology and Venereology, Podiatry, Infectious diseases, or Family and community medicine.
Diagnosis
The diagnosis of blistering diseases is carried out using the following procedures:
- Medical history: a clinical history is obtained, including the patient’s medical and family history, symptoms, and lifestyle.
- Physical examination: the area where the blisters have appeared is examined to assess their characteristics. Other areas of the skin and mucous membranes are also evaluated for additional lesions.
- Biopsy: useful for detecting autoimmune blistering diseases. A sample of damaged tissue is collected and analyzed in the laboratory using direct immunofluorescence, a technique that uses a fluorochrome-labeled antibody to detect IgG antibodies (which protect against bacterial infections) or IgA antibodies (which protect mucous membranes and body fluids against infections).
- Indirect immunofluorescence: a blood sample is analyzed to detect specific antibodies. Two antibodies are used: the primary antibody binds to the antigen, while the secondary fluorescent antibody binds to the primary antibody, enabling easy detection.
- Immunoblotting: molecular biology technique used to diagnose the specific disease affecting the patient. To identify the type of antibodies produced by the body, proteins are separated according to molecular weight, and primary and secondary antibodies are added in order to visualize the bands formed upon binding.
Treatment
The main recommendation is not to touch blisters and to allow them to heal on their own in order to prevent discomfort and infection. Friction against the damaged area should be avoided as much as possible, and the area should preferably be left uncovered.
If the blister causes significant pain or there is a risk of spontaneous rupture, the fluid should be drained following these recommendations:
- Wash hands with soap and water before handling the bullae.
- Clean the affected area with warm water and mild soap.
- Disinfect a needle with alcohol or hydrogen peroxide.
- Puncture one edge of the blister to allow the fluid to drain out.
- It is important to allow the fluid to drain spontaneously, without squeezing the blister and, above all, without removing the overlying skin.
- Once all the fluid has drained, wash the blister again.
- Apply an antibiotic cream.
- Cover with a sterile gauze dressing, which should be changed regularly to prevent contamination or moisture accumulation, as this may delay healing or facilitate bacterial growth.
Treatment of blistering diseases depends on their nature. Since most cases are infectious processes, antibiotics are prescribed to combat bacteria and analgesics are used to relieve pain.
