Positivity criteria were defined by the occurrence of clinical objective signs, such as urticaria, angioedema, rash, bronchospasm, hypotension, oxygen saturation below 90% or 20% fall in FEV1, one study also mentioned a 20% change in heart rate.3,17 Immediate HSRs with delayed onset may occur with PPIs.18 Most PPIs are slow-release and dose titration is challenging due to the formulation and potential loss of drug function. Consequently, the TF suggests prolonged observation of ≥3 hours after the last step of an oral DPT with PPI.