Delayed patch test reading after 5 days: The Mayo Clinic experience

The Relevance of 7-Day Patch Test Reading

“…The terminology used internationally varies, with the North American Contact Group referring to standard 48-and 96-hour readings as day 3 and 5, while various European Groups studies refer to these readings as day 2 and 4. 4,5 In addition, different concentrations of allergens are used, such as methylchloroisothiazolinone/methylisothiazolinone 0.02% used by the BSCA and Swedish Contact Groups and 0.01% by the North American Contact Group. Similarly, many American groups test with nickel sulfate 2.5%, whereas European centers use 5%.…”

Patch Testing for Metal Allergy With Manufacturer-Supplied Materials Before Nuss Bar Insertion

“…Studies have shown that reactions to metals can become positive up to 168 hours after initial patch placement. 18,20,21 In their study, Jonker and Bruynzeel 20 compared patch test readings at 48 and 72 hours with readings at 144 and 168 hours. They found that 8.2% of patients displayed late positive reactions at 144 or 168 hours to certain allergens including nickel sulfate.…”

Response to: Can patch test sensitization with gold sodium thiosulfate be ruled out?—A case report

“…However, gold sodium thiosulfate (GST) is a well-described, specifically noted exception to the above definition. 3 This normal delayed reaction pattern is well described, 4 including in known GST-allergic subjects who are incapable of being actively sensitized. 5 A late reaction to GST is a positive reaction to GST, not a "negative reaction followed by a flare".…”