Oral Challenge without Skin Testing Safely Excludes Clinically Significant Delayed-Onset Penicillin Hypersensitivity

Area of Science:

• Clinical immunology
• Pharmacology
• Allergy and immunology

Background:

• Penicillins are frequently implicated in hypersensitivity reactions.
• Current guidelines suggest penicillin skin tests (ST) before re-administration for nonimmediate reactions (NIR).

Purpose of the Study:

• To evaluate the necessity of ST prior to penicillin re-administration in patients with a history of NIR.
• To determine if an oral challenge alone is sufficient for penicillin allergy assessment.

Main Methods:

• Patients with NIR underwent penicillin ST, but results were disregarded for subsequent oral challenges.
• A graded oral penicillin challenge (1/10th dose to full dose over 5 days) was administered.
• Patients continued a 5-day course of the full therapeutic dose at home.

Main Results:

• Out of 642 patients with alleged penicillin allergy, 96.1% completed an oral challenge.
• Immediate reactions occurred in 1.5% of patients, irrespective of ST results (P = .7).
• Late reactions and mild reactions during home challenge were observed in 4% and 6.1% of patients, respectively, regardless of ST outcomes.

Conclusions:

• A 5-day oral penicillin challenge is a safe and sufficient method to exclude penicillin allergy after NIR.
• Preceding skin tests are not necessary for penicillin allergy assessment in patients with NIR.