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Different types (and timing) of drug allergic (allergy) reactions

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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Signs and allergic patterns of suspected drug allergy with timing of onset

Immediate, rapidly evolving reactions

  • Anaphylaxis - a severe multi-system reaction characterised by:
    • erythema, urticaria or angioedema and
    • hypotension and/or bronchospasm
  • Urticaria or angioedema without systemic features
  • Exacerbation of asthma (for example, with non-steroidal anti-inflammatory drugs [NSAIDs])

Onset usually less than 1 hour after drug exposure (previous exposure not always confirmed)

Non-immediate reactions without systemic involvement

  • Widespread red macules or papules (exanthema-like)
  • Fixed drug eruption (localised inflamed skin)

Onset usually 6-10 days after first drug exposure or within 3 days of second exposure

Non-immediate reactions with systemic involvement

Drug reaction with eosinophilia and systemic symptoms (DRESS) or drug hypersensitivity syndrome (DHS) characterised by:

  • widespread red macules, papules or erythroderma
  • fever
  • lymphadenopathy
  • liver dysfunction
  • eosinophilia

Onset usually 2-6 weeks after first drug exposure or within 3 days of second exposure

Toxic epidermal necrolysis or Stevens-Johnson syndrome characterised by:

  • painful rash and fever (often early signs)
  • mucosal or cutaneous erosions vesicles, blistering or epidermal detachment
  • red purpuric macules or erythema multiforme

Onset usually 7-14 days after first drug exposure or within 3 days of second exposure

Acute generalised exanthematous pustulosis (AGEP) characterised by:

  • widespread pustules
  • fever
  • neutrophilia

Onset usually 3-5 days after first drug exposure

Common disorders caused, rarely, by drug allergy:

  • eczema
  • hepatitis
  • nephritis
  • photosensitivity vasculitis

Time of onset variable

With respect to DRESS, study evidence (2) found:

  • most common drug causes were found to be antibiotics (74%) and anticonvulsants (21%)
  • most common comorbidities were epilepsy (26%) and hypertension (26%)

Reference:


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The content herein is provided for informational purposes and does not replace the need to apply professional clinical judgement when diagnosing or treating any medical condition. A licensed medical practitioner should be consulted for diagnosis and treatment of any and all medical conditions.

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