Skin blisters

A clear guide to understanding what blisters are, why they appear, and in what cases they cease to be a minor problem.

Summary in 60 seconds

• Blisters are raised lesions of the skin that contain fluid.
• When they are small they are called vesicles; when they are larger, they are called ampullae or bullae.
• Many appear due to friction, pressure, humidity, heat, or minor burns.
• Others are related to eczema, contact dermatitis, infections, or autoimmune diseases.
• The location, number of lesions, and the presence of pain, itching, or fever greatly influence the diagnosis.
• An isolated blister on the heel is not the same as multiple lesions on the torso, mouth, or genitals.
• Friction blisters usually resolve with protection and local care.
• However, if they appear without a clear cause, are numerous, or affect mucous membranes, it is important to consult a specialist.
• The urgency increases if there is fever, poor general condition, or skin detachment.

What are they?

A blister is a raised area of skin filled with fluid. In dermatology, the term vesicle is usually used for small lesions, and bulla or blister for larger ones. The fluid may be clear, yellowish, bloody, or cloudy if it becomes infected (DermNet 2023) .

More than a disease in itself, a blister is a type of skin reaction . It can be due to simple causes, such as a graze, or be part of inflammatory, infectious, drug-induced, or autoimmune processes (DermNet 2023 ).

Why do they appear?

Blisters appear when various irritants separate layers of skin and fluid accumulates in the space. The most frequent causes in daily life are repeated friction, pressure, humidity, heat, and minor burns (DermNet 2023 ).

They can also appear in inflammatory conditions such as contact dermatitis and dyshidrotic eczema , which usually cause small, very itchy vesicles on the hands and feet BAD 2025 AAD 2020 .

Among the infectious causes are herpes simplex , herpes zoster , chickenpox and bullous impetigo CDC 2024 CDC 2024b .

In a less frequent group, blisters are associated with specific diseases such as bullous pemphigoid , pemphigus , dermatitis herpetiformis , epidermolysis bullosa or severe drug reactions such as Stevens-Johnson syndrome/toxic epidermal necrolysis AAD 2021 Murrell 2020 .

Not every blister is caused by friction or local trauma: the location, pain, itching, and involvement of mucous membranes completely change its clinical significance.

What do they look like?

Appearance can be quite helpful. A friction blister is usually isolated, tense, and painful , in areas of friction such as heels, toes, or palms (DermNet 2023 ).

In dyshidrotic eczema , small, deep vesicles predominate, accompanied by intense itching , especially on the hands and feet AAD 2020 .

In herpes simplex, grouped vesicles are usually seen; in herpes zoster, painful vesicular lesions are seen in a unilateral distribution ; and in bullous pemphigoid, tense blisters are seen on healthy or reddened skin, often with prior itching CDC 2024b Draft 2022 .

It also matters whether the blister is intact or ruptured, whether it leaves erosions or scabs, and whether it affects the mouth, eyes, or genitals. This clinical pattern can completely change the diagnostic suspicion (DermNet 2023) .

In what diseases or conditions do they usually occur?

(This order is for guidance only. There is no universal ranking because it depends on age, the affected area, and the clinical context.)

1. Very frequent

• Friction or chafing blisters
• Minor or sunburns
• Contact dermatitis
• Dyshidrotic eczema

These causes account for a large part of the cases seen in general practice, especially when the lesions are localized and the context is clear DermNet 2023 BAD 2025 .

2. Frequent

• Herpes simple
• Shingles
• Bullous impetigo
• Chickenpox

They are usually suspected due to the distribution, pain, grouped nature of the lesions or the presence of contagion and associated symptoms CDC 2024 CDC 2024b .

3. Infrequent

• Bullous pemphigoid
• Pemphigus
• Dermatitis herpetiformis
• Epidermolysis bullosa
• SJS/TEN and other severe skin reactions to medications

They are less common, but clinically important due to their diagnostic complexity and, in some cases, their severity Murrell 2020 Reunala 2021 .

When should I consult?

Consult a specialist if any of these situations occur:

• The blister is very painful or appears without a clear cause.
• There is pus, progressive redness, local heat, or a bad odor.
• The injuries affect the eyes, mouth, genitals, or eyelids.
• Many blisters appear in a short time or are very widespread.
• They are accompanied by fever, weakness, or significant discomfort.
• They started shortly after a new medication.
• The affected person is an infant, a frail elderly person, or someone immunocompromised.

These situations may indicate infection, autoimmune blistering disease or a relevant drug reaction NHS 2023 BAD 2023 .

When there is fever, involvement of the eyes, mouth or genitals, the problem is no longer minor and deserves prompt medical evaluation.

What NOT to do?

• Don’t pop the blister. The skin covering it protects the area and reduces the risk of infection (NHS 2023 ).
• Do not apply irritating products without knowing the cause. Alcohol, homemade mixtures, or «drying» substances can worsen the problem . BAD 2025 .
• Do not minimize blisters if there is also fever, severe pain or affected mucous membranes BAD 2023 .
• Don’t assume all blisters are allergies or burns. The clinical context greatly influences the diagnosis (DermNet 2023 ).

What does a dermatologist usually do?

The dermatologist usually begins with a detailed medical history : onset, symptoms, location, triggering factors, new products, recent medications, presence of fever, history of eczema, herpes or autoimmune diseases DermNet 2023 .

Next, examine the morphology and distribution of the lesions. Depending on the case, you may request a culture , viral swab , skin biopsy , direct immunofluorescence , or patch tests (Murrell 2020, Borradori 2022 ).

When there is extensive involvement, significant pain, compromised mucous membranes or suspicion of a severe drug reaction, evaluation should be a priority BAD 2023 .

Frequently Asked Questions

Is it better to leave the blister intact?

• In general, yes. Maintaining the skin cover helps protect the underlying skin while it heals (NHS 2023) .

Are all blisters contagious?

• No. Friction blisters, burns, eczema, or bullous pemphigoid are not contagious. Some infections, such as herpes, impetigo, or chickenpox, can be. (DermNet 2023, CDC 2024 )

Are blisters on hands and feet usually eczema?

• Sometimes, but not always. Friction blisters are also common in these locations. Medical history and recurrence help to differentiate them (AAD 2020 ).

When should you suspect shingles?

• When pain, burning or tingling appears and then a rash with vesicles appears on a unilateral strip of the body or face CDC 2024b .

Can they go out to get medication?

• Yes. Some drugs can trigger blistering rashes, including severe reactions that require urgent care (BAD 2023 ).

Is a blister that itches a lot usually less serious?

• Not necessarily. Intense itching can be seen in contact dermatitis, dyshidrotic eczema, dermatitis herpetiformis, or bullous pemphigoid (Reunala 2021 Borradori 2022 ).

Bibliography and sources

• DermNet New Zealand. Blistering skin conditions [Internet] . 2023 [citado 19 abr 2026] . Available at: https://dermnetnz.org/topics/blistering-skin-conditions
• DermNet New Zealand. Friction blister [Internet] . 2023 [citado 19 abr 2026] . Available at: https://dermnetnz.org/topics/friction-blister
• National Health Service. Blisters [Internet] . 2023 [citado 19 abr 2026] . Available at: https://www.nhs.uk/conditions/blisters/
• American Academy of Dermatology Association. Dyshidrotic eczema: overview [Internet] . 2020 [citado 19 abr 2026] . Available at: https://www.aad.org/public/diseases/eczema/types/dyshidrotic-eczema
• British Association of Dermatologists. Contact dermatitis [Internet] . 2025 [citado 19 abr 2026] . Available at: https://www.bad.org.uk/pils/contact-dermatitis
• Centers for Disease Control and Prevention. Chickenpox symptoms and complications [Internet] . 2024 [citado 19 abr 2026] . Available at: https://www.cdc.gov/chickenpox/signs-symptoms/index.html
• Centers for Disease Control and Prevention. Clinical features of shingles (herpes zoster) [Internet] . 2024 [citado 19 abr 2026] . Available at: https://www.cdc.gov/shingles/hcp/clinical-signs/index.html
• American Academy of Dermatology Association. Bullous pemphigoid: overview [Internet] . 2021 [citado 19 abr 2026] . Available at: https://www.aad.org/public/diseases/az/bullous-pemphigoid-overview
• Murrell DF, Peña S, Joly P, Marinovic B, Hashimoto T, Diaz LA, et al. Diagnosis and management of pemphigus: recommendations of an international panel of experts. J Am Acad Dermatol. 2020;82(3):575-85.e1. Available at: https://pubmed.ncbi.nlm.nih.gov/29438767/
• Borradori L, Van Beek N, Feliciani C, Tedbirt B, Antiga E, Bergman R, et al. Updated S2K guidelines for the management of bullous pemphigoid initiated by the European Academy of Dermatology and Venereology. J Eur Acad Dermatol Venereol. 2022. Available at: https://pubmed.ncbi.nlm.nih.gov/35766904/
• Reunala T, Salmi TT, Hervonen K, Kaukinen K, Collin P. Dermatitis herpetiformis: an update on diagnosis and management. Am J Clin Dermatol. 2021;22(3):329-38. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC8068693/
• Has C, Bauer JW, Bodemer C, Bolling MC, Bruckner-Tuderman L, Diem A, et al. Consensus reclassification of inherited epidermolysis bullosa and other disorders with skin fragility. Br J Dermatol. 2020;183(4):614-27. Available at: https://pubmed.ncbi.nlm.nih.gov/32017015/
• British Association of Dermatologists. SJS/TEN [Internet] . 2023 [citado 19 abr 2026] . Available at: https://www.bad.org.uk/pils/sjs-ten
• National Institute of Arthritis and Musculoskeletal and Skin Diseases. Epidermolysis bullosa [Internet] . 2023 [citado 19 abr 2026] . Available at: https://www.niams.nih.gov/health-topics/epidermolysis-bullosa