Background Anaphylactic reactions to fig fruits (Ficus carica) have been reported from subjects sensitized to Ficus benjamina (FB) latex allergens. Figs may also be involved in the latex–fruit syndrome.
Objective To study the immunologic relationship between fig fruit, Ficus benjamina, natural rubber latex (Hevea brasiliensis), and other tropical fruits.
Methods RAST inhibition and Western blotting with FB and fruit extracts was performed in five patients with oral allergy syndrome (OAS) or anaphylaxis after the ingestion of figs and one patient with symptoms from exposure to FB trees. Co-sensitization to rubber latex and tropical fruits (kiwi, banana, avocado, papaya, pineapple, mulberry) was studied by skin testing.
Results RAST to FB was inhibited >95% by FB extracts and 16–65% (mean 49%) by extracts from fresh fig. RAST to fig fruit was inhibited >95% by FB and fresh fig, 63–97% (mean 86%) by dried fig, and 0–84% (mean 35.5%) by kiwi fruit. FB and fig extracts lost most of their allergenicity when denatured by heat (95 °C) or reduced by dithiothreitol. Western blotting after non-reducing gel electrophoresis revealed IgE binding to proteins of 22 and 28–34 kDa in FB latex; however, no corresponding allergens could be detected in fig extracts. Positive skin tests were obtained most often with kiwi fruit, papaya, and avocado. Sensitization to rubber latex could not be demonstrated in any of the patients. RAST to papain was positive in three of five patients.
Conclusions Allergic reactions to fresh or dried figs can present as a consequence of primary sensitization to airborne FB allergens independent of sensitization to rubber latex allergens. Kiwi fruit, papaya, and avocado as well as pineapple and banana may be other fruits associated with sensitization to Ficus allergens.