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

Last edited 04/2022 and last reviewed 04/2022

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:

Related pages:

drug allergy

anaphylaxis