Contact Allergies Can Be Missed by Not Performing Delayed Patch Test Readings

Patch test results read too soon may miss delayed reactions.

Patients with suspected contact allergies frequently undergo patch testing in an attempt to identify the causative agent. In this procedure, chemicals are applied for 48 hours, after which the skin is examined for positive reactions. It is standard practice to examine the patch test sites for reactions 48 to 96 hours after they were originally applied. However, it has been reported that some allergens have a delayed reaction. The purpose of this study was to determine the frequency of positive patch tests that become apparent at 1 week, when the reactions were negative at earlier time points.

A total of 203 patients older than 14 years were patch tested to the British Society for Cutaneous Allergy standard series and, as appropriate, other s…

Reviewing Author

Craig A. Elmets, MD

Disclosures

Consultant / Advisory board Astellas Pharmaceuticals

EquityVaxin

Grant / Research support NIH; NIH/NCI; Veteran’s Administration; Ferndale Laboratories; Kyowa Hakko Kirin Pharma, Inc.

Editorial boards Cancer Prevention Research; Photodermatology, Photoimmunology, & Photomedicine; UpToDate; eMedicine; Journal of Dermatological Sciences; JAMA Dermatology

Leadership positions in professional societies American Academy of Dermatology (Vice Chair, Committee on Science and Research); Photomedicine Society (Board of Directors)