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.