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Drug reactions can be immediate or delayed, and can be allergic or non-allergic.
Clinical history and documentation of the reaction is paramount.
For patients with suspected drug allergy document in the medical records
Document all new reactions promptly and thoroughly to assist in future investigation.
Immediate, rapidly evolving reactions
Anaphylaxis – a severe multi system reaction characterised by:
|
Onset usually less than 1 hour after drug exposure (previous exposure not always confirmed) |
Urticaria or angioedema without systemic features | Onset usually less than 1 hour after drug exposure (previous exposure not always confirmed) |
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) |
Onset usually 6–10 days after first drug exposure or within 3 days of second exposure |
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:
|
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:
|
Onset usually 7–14 days after first drug exposure or within 3 days of second exposure |
Acute generalised exanthematous pustulosis (AGEP) characterised by:
|
Onset usually 3–5 days after first drug exposure |
A drug reaction is more likely if it occurred during or after use of the drug and:
A drug reaction is less likely if:
When a person presents with new suspected drug allergy, document their reaction in a structured approach (NICE guidance recommendation 1.2.3) including:
None recommended prior to referral.
Specific IgE (RAST) testing to drugs should not be used in a non-specialist setting (NICE guidelines).
All information regarding reactions, timing and implicated drugs must be included in the referral.
e-Referral Selection
BSACI guidelines for management of drug allergy: onlinelibrary.wiley - for the management of drug allergy
NICE Drug allergy: diagnosis and management:
NICE guidelines CG183
This guideline has been signed off by South Devon and Torbay CCG
Publication date: August 2017