Allergy to carminic acid: in vitro evidence of involvement of protein-binding hapten.

We previously described a rare case of anaphylaxis presumably induced by carminic acid in cochineal dye used as a food additive. In this study, highly pure carminic acid was added to an albumin-containing buffer at various concentrations, followed by serial dilution. Varying the mixing ratio of carminic acid and albumin affected the extent of histamine release from passively sensitized basophils. Similar basophil histamine release occurred with carminic acid-globulin solutions. These results provide experimental evidence indicating that basophil activation is dependent on hapten (carminic acid) and carrier (protein) interaction.