How should a skin blister be evaluated and managed, including assessment of size, location, infection risk, and appropriate treatment options?

Evaluation and Management of Skin Blisters

For simple friction or pressure blisters that are asymptomatic and non-inflammatory, leave them completely intact and observe; for pressure-painful blisters, pierce at the base with a sterile needle to drain while preserving the blister roof as a biological dressing. 1, 2, 3

Initial Assessment

Key Clinical Features to Document

• Size and extent: Measure percentage of body surface area (BSA) involved using a body map 1
• Location: Note if blisters are on palms/soles (more likely to require drainage), mucous membranes (suggests serious pathology), or widespread distribution 1, 3
• Blister characteristics: Assess for tense vs flaccid blisters, presence on erythematous vs normal skin, and whether blisters are intact or ruptured 1
• Associated symptoms: Document skin pain, fever, malaise, or involvement of eyes, mouth, genitals, or other mucous membranes 1
• Medication history: Record all drugs taken in the previous 2 months, including over-the-counter medications, as drug reactions are a critical differential 1

Physical Examination Priorities

• Examine all mucous membranes (eyes, mouth, nose, genitals, perianal area) for erosions or blisters 1
• Check vital signs and assess for signs of systemic illness 1
• Test for Nikolsky sign (lateral pressure causing skin sloughing) if autoimmune disease suspected 1
• Look for pustules, dusky erythema, or areas of epidermal detachment 1

Management Algorithm Based on Clinical Presentation

Simple Friction/Pressure Blisters (<10% BSA, Asymptomatic)

• Leave intact blisters completely alone if they are not causing pressure pain 2, 3
• Apply observation only with no intervention required 1, 4
• If pressure-painful or interfering with function, proceed to drainage technique below 1, 4

Drainage Technique for Symptomatic Intact Blisters

1. Gently cleanse with antimicrobial solution without rupturing the blister 1, 2, 4
2. Pierce at the base with a sterile needle (bevel facing up), selecting a site where gravity will facilitate drainage 1, 2
3. Apply gentle pressure with sterile gauze to drain fluid completely 1, 4
4. Never deroof the blister—the roof serves as a natural biological dressing that reduces infection risk and promotes healing 1, 2, 5, 4
5. Cleanse again after drainage with antimicrobial solution 1
6. For large blisters, use a larger needle and pierce multiple times if needed 1

Already-Ruptured Blisters

• Leave remnants of blister roof in place if no signs of infection 5, 4
• Remove blister roof only if clinical signs of infection are present (increased erythema, purulent discharge, fever, worsening pain) 5, 4
• Apply bland emollient (50% white soft paraffin and 50% liquid paraffin) to support barrier function 1, 2, 4
• Cover with non-adherent dressing if needed for protection 1, 5, 4

Extensive or Concerning Blisters Requiring Specialist Evaluation

Red flags mandating urgent dermatology consultation:

• Blisters covering 10-30% BSA 1, 4
• Symptomatic bullae or erosions on skin or mucous membranes 1
• Blisters on erythematous or urticarial base suggesting autoimmune disease 1
• Associated systemic symptoms (fever, malaise, respiratory symptoms) 1
• Non-healing single bulla without clear traumatic cause 5

For blisters >30% BSA:

• Immediate hospitalization required 4
• Initiate IV fluid resuscitation and establish venous access through non-lesional skin 1
• Administer IV methylprednisolone 1-2 mg/kg if autoimmune bullous disease suspected 1
• Monitor for fluid/electrolyte abnormalities 1

Infection Prevention and Management

Daily Wound Care

• Change dressings using aseptic technique to prevent secondary infection 1, 5, 4
• Perform daily washing with antibacterial products to reduce colonization 1, 4
• Document daily the number, size, and location of blisters on a chart 1, 2, 5

When to Obtain Cultures and Start Antibiotics

• Obtain bacterial cultures before initiating antibiotics if signs of infection present (erythema, purulent discharge, fever) 2, 5
• Use systemic antibiotics only for local or systemic signs of infection, not prophylactically 1, 2
• Consider semi-synthetic penicillin, first-generation cephalosporin, or clindamycin for mild infection 5

Diagnostic Workup for Unclear or Extensive Cases

Laboratory Testing

• Skin biopsy from lesional skin for histopathology 1, 5
• Second biopsy from perilesional skin for direct immunofluorescence to exclude autoimmune bullous disease 1, 5
• Complete blood count, liver/kidney function, electrolytes if systemic involvement 1
• Bacterial swabs for culture and sensitivity 1
• Consider mycoplasma serology and chest X-ray if infection suspected 1

Differential Diagnosis Considerations

The most critical distinctions are between:

• Simple friction/pressure blisters (benign, local care only) 3, 6
• Autoimmune bullous diseases (bullous pemphigoid, pemphigus vulgaris—require immunosuppression) 1, 7
• Drug-induced blistering (Stevens-Johnson syndrome/toxic epidermal necrolysis—requires immediate drug cessation and hospitalization) 1
• Infectious causes (bullous impetigo, necrotizing fasciitis—require antibiotics) 5, 8

Pain Management

• Offer analgesia prior to dressing changes, as patients commonly report burning or pain during blister care 1, 2
• Use acetaminophen or NSAIDs for routine pain control 4
• Consider involvement of pain team for extensive erosions 1

Common Pitfalls to Avoid

• Never deroof intact blisters—the roof is protective and promotes healing 1, 2, 5, 4
• Do not apply topical antimicrobials prophylactically—reserve for clinically infected areas only 1, 2
• Do not delay specialist referral for blisters with mucous membrane involvement or >10% BSA 1
• Reassess within 24-48 hours if managed as outpatient to ensure appropriate response 2, 5