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 protein-aceous 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.