Discussion
Allergy to cocoa is rare, but cocoa has been reported previously as both an occupational and food allergen. A survey of Salvadorian schoolchildren demonstrated an incidence of cocoa allergy between 0.5-0.7%, they report symptoms including sneezing, rhinorrhea, wheezing, hives; however most of these cases have not been objectively demonstrated.4
In another study, 40 occupational cocoa workers had a high prevalence of positive skin tests to cocoa powder extract (60.2%) compared to the unexposed population, and 2 out of 3 sensitized subjects with bronchoconstriction-related underwent a bronchoprovocation test to cocoa powder with objective changes in FEV1. These suggest that workers employed in cocoa processing are at risk of developing allergic sensitization and respiratory impairment. 5
As allergy to chocolate and cocoa is commonly attributed to the presence of other allergenic sources that often accompany cocoa in manufactured foods, such as tree nuts or milk, Lopes et al . confirmed specific cocoa allergy in 3 patients via supervised oral challenges and suggested raised awareness for cocoa as a potential true food allergy.2
To date, no major cocoa allergen has been defined, although there are studies of cocoa bean proteins 6 as well as a publication identifying a potential allergen belonging to the PR-10 group.7
Pereira Menezes et al, to demonstrate the allergenic nature of TcPR-10 protein in a mouse model, modified by genetic engineering the allergenic motif of this protein trying to reduce its allergenic character.8
Cocoa bean 2S Albumin storage polypeptides have been described that have high sequence similarity (>52%) to several 2S albumins from known allergenic sources such as English walnut, rape seed and Brazil nut.9
Assuming that primary sensitization was produced by tree nuts proteins, we would expect a total inhibition of IgE binding (which could not be observed in our study), however, our inhibition studies demonstrated cross-reactivity between cocoa, walnuts and almond proteins.
We hypothesize that primary tree nut allergy predisposed our patient to develop an allergy cocoa.