Algorithm to identify patients at low risk

for penicillin/beta-lactam allergy

Was this the first ever ingestion of a beta-lactam antibiotic, and did the symptoms occur within 10 days of the initial dose?

Yes

No

Clinical Pearl:

It takes a minimum of 10 days for an adequate amount of IgE to develop after a first ever exposure to a drug to cause type I immediate hypersensitivity reaction. It takes a similar amount of time to develop drug specific T cells that can cause a type IV hypersensitivity reaction. Therefore, symptoms and rashes that develop in the first 10 days after the first ever exposure to a class of antibiotics are due to the underlying infection, or some other medication, and not caused by a new antibiotic.