Clinical images - Diagnosing a blistering rash

Use these pictures to differentiate shingles, pemphigus, pemphigoid and insect bite rashes. By Dr Nigel Stollery



  • Can occur at any age in patients who have had varicella
  • Vesicular eruption affecting whole or part of a single dermatome
  • Pain often precedes rash formation
  • Pain may last long after rash clears (post-herpetic neuralgia)
  • Further episodes may occur
  • In those who are not immune, varicella may develop after contact with shingles


  • In young, fit patients, analgesia may be all that is required
  • Antiviral treatment, such as aciclovir, can be helpful

Bullous pemphigoid


  • Usually occurs in the elderly
  • Blisters are tense and may be blood filled
  • Often affects flexures
  • Oral blisters may occur but are rare
  • Patients usually otherwise well
  • Nikolsky's sign (when rubbing results in exfoliation of top layer of skin) is negative


  • Treatment includes oral steroids and immunosuppressant drugs
  • Dose can often be reduced quite quickly
  • Usually settles with time and treatment can be stopped


Bullous pemphigus


  • Usually occurs in middle age
  • Affects trunk, flexures and scalp
  • Occurs in those with otherwise poor health
  • May be associated with malignancy, including undiagnosed tumours
  • Blisters are superficial and flaccid
  • Severe, often life-threatening condition
  • Nikolsky's sign is positive


  • Treatment includes oral steroids and immunosuppressant drugs
  • Treatment can be difficult
  • Treatment is usually very prolonged

Insect bite


  • Single or multiple vesicles, usually in a cluster
  • Often intensely itchy
  • Urticaria may precede appearance of the vesicle
  • If recurrent, insect repellents may decrease risk of further bites


  • Oral or topical antihistamines will decrease itching
  • Secondary bacterial infection may occur
  • In more severe cases, topical or oral steroids can be helpful
  • Rarely, anaphylaxis may develop (especially to wasp stings)

Dr Stollery is a GP in Kibworth, Leicestershire, and clinical assistant in dermatology at Leicester Royal Infirmary.

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