Background: There have been several reports of carmine allergy; however, identification of the responsible carmine allergens has not been widely documented.
Methods: Three female patients presented with a history of anaphylaxis and/or urticaria/angioedema after ingestion of carmine-containing foods. All three patients had 4+ skin prick tests to carmine. Among them, two patients were confirmed to have carmine allergy by blinded, placebo-controlled food challenges to carmine. SDS–PAGE of cochineal insects and carmine, immunoblotting for IgE antibody with sera from all three patients, and immunoblotting inhibition with carmine were performed.
Results: SDS–PAGE of minced cochineal insects revealed several protein bands of 23–88 kDa. Several of these bands were variably recognized by our three patients' sera, and this reactivity was inhibited by carmine. Although no protein bands could be visualized on SDS–PAGE of carmine in Coomassie brilliant blue staining, three protein bands were recognized by two of the three patients' serum.
Conclusions: These results suggest that commercial carmine retains proteinaceous material from the source insects. These insect-derived proteins (possibly complexed with carminic acid) are responsible for IgE-mediated carmine allergy. Patient reactivity to these proteins may vary.