BACKGROUND Since the spring of 2020, we have seen several patients experiencing severe allergic contact dermatitis (ACD) from the Dexcom G6 glucose sensor after the composition of the sensor's adhesive patch had been changed. We have previously reported the finding of a new sensitizer, 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate, in the Dexcom G6 adhesive patch. Three patients with ACD from Dexcom G6 tested positive to this sensitizer. They were also allergic to isobornyl acrylate, a sensitizer present both in Dexcom G6 and in other medical devices previously used by these patients. OBJECTIVE The aim of the study was to report the first 4 cases sensitized to 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate without a simultaneous allergy to isobornyl acrylate. METHODS The cases were patch tested their own materials, a medical device series, and 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate in several concentrations. RESULTS All 4 cases tested positive to 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate at either 1.0% or 1.5% in petrolatum, whereas 20 controls tested negative to both concentrations. CONCLUSIONS The cases reported here provide further evidence of 2,2'-methylenebis(6-tert-butyl-4-methylphenol) monoacrylate as a relevant culprit sensitizer in patients with ACD from Dexcom G6. However, the initially used patch test concentration (0.3%) did not suffice to elicit positive reactions in these cases, which is why patch testing at 1.5% is recommended.