VHOSPITAL.CLINIC · Differential Diagnosis
Cellulitis vs Shingles (Herpes Zoster)
Clinical comparison — shared symptoms, key differences, distinguishing diagnostic tests, treatment pathways, and when to seek urgent evaluation.
Condition Overview
Condition A
Cellulitis
Cellulitis is a bacterial skin infection causing redness, warmth, swelling, and tenderness of the skin and underlying tissue. Streptococcus and Staphylococcus are the most common causes; it requires prompt antibiotic treatment.
Condition B
Shingles (Herpes Zoster)
Shingles is reactivation of the varicella-zoster virus (chickenpox virus) in sensory nerves, causing a painful, blistering rash in a dermatomal distribution. Post-herpetic neuralgia is a common and debilitating complication.
Shared Symptoms — Why They're Confused
Both conditions present with 3 overlapping symptoms, making clinical differentiation essential.
Key Clinical Differences
Cellulitis
- Spreading unilateral erythema, warmth, swelling, tenderness
- Systemic fever and raised inflammatory markers
- No vesicles in early cellulitis
- Usually lower leg; S. aureus or Streptococcus cause
Shingles (Herpes Zoster)
- Dermatomal unilateral vesicular rash with burning pain
- Pain often precedes rash by 2–4 days (prodrome)
- Lesions follow a dermatome — does not cross midline
- VZV reactivation from dorsal root ganglion
Distinguishing Diagnostic Tests
| Test | Cellulitis | Shingles (Herpes Zoster) |
|---|---|---|
| Rash morphology | Non-vesicular erythema — no blisters in early cellulitis | Grouped vesicles on erythematous base in a dermatomal strip |
| Dermatomal distribution | Not dermatomal — spread without anatomical border | Strictly dermatomal — follows nerve root distribution, stops at midline |
| Pain character | Dull aching pain over erythematous area | Neuropathic burning pain preceding rash; allodynia |
Treatment Approaches
Cellulitis
- •IV/oral flucloxacillin or co-amoxiclav
- •Elevation and analgesia
- •Mark lesion border to monitor spread
Shingles (Herpes Zoster)
- •Valaciclovir or aciclovir within 72 h of rash
- •Analgesics; consider pregabalin for neuropathic pain
- •Postherpetic neuralgia prevention with early treatment
When Doctors Consider Each Diagnosis
🔵 Consider Cellulitis when:
- →Non-vesicular spreading erythema, no dermatomal limit, S. aureus aetiology
🟢 Consider Shingles (Herpes Zoster) when:
- →Dermatomal vesicles, burning prodrome, stops at midline, VZV cause
Explore Each Condition in Detail
Related Clinical Pages
Cellulitis
Medical References
Content on this page is informed by evidence-based clinical sources including:
- World Health Organization (WHO)Global health guidance and disease classification
- National Health Service (NHS)UK clinical guidelines and patient information
- National Institute for Health and Care Excellence (NICE)Evidence-based clinical practice guidelines
- Centers for Disease Control and Prevention (CDC)US public health data and clinical recommendations
- PubMed – NCBIPeer-reviewed biomedical literature and clinical studies
- Cochrane LibrarySystematic reviews and meta-analyses in evidence-based medicine
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