Carob is not allergenic in peanut-allergic subjects

The antigenic potential of proteins from the carob bean, a member of the legume family used as a food additive, have not so far been investigated and legumes share antigenic proteins with peanut, a potent trigger of anaphylaxis.

To assess the carob protein determinants of sensitization in peanut-allergic children.

In a prospective, double-blind, placebo-controlled study 12 patients (median age 9.5 years) with a history of hyperreactivity to peanut (anaphylaxis) were assessed. Skin prick tests with a commercial peanut allergen, raw carob pulp, raw and cooked carob cotyledon formula were used to confirm the history. RAST for peanuts and cooked carob were used to evaluate sensitization to these proteins. Carob-specific IgE were identified by immunoblotting analyses. Allergic reactivity was evaluated during double-blind placebo-controlled food challenges (DBPCFC; 5.5 g carob extract and cooked carob cotyledon formula).

Peanut allergen-induced skin prick test positivity in all children (confirmed during double-blinded challenge in 6/12 patients), carob pulp in 3/12 patients, raw carob bean in 6/12, and cooked carob cotyledon formula in none. RAST were positive for peanut in all cases but negative for carob beans in 9/12 cases. Immunoblot analyses found peanut-specific IgE in all cases and raw carob bean-specific IgE in eight cases. Carob allergens were identified in the 17.5, 48, and 66 kDa MW bands. The least allergenic density was found for cooked carob proteins. There was no clinical reactivity with either raw or cooked carob during DBPCFC.

These data suggest that carob-specific sensitization, apparent both in vitro and in SPTs, can be concordant with peanut allergy and that cooked carob can be ingested by children who are allergic to peanuts. That heat-processing deactivates carob protein allergenicity has dietary implications for polyallergic children.