Oral allergy syndrome to fig

The few cases of food allergy to fig reported to date, whose main manifestations were anaphylactic reactions, have been related to a cross-sensitisation to weeping fig (Ficus benjamina) or to the 'latex-fruit syndrome'. Here we report on two cases of the oral allergy syndrome (OAS) to fig in patients whose main allergic manifestations were related to sensitisation to grass and birch pollens.

The patients were characterised by clinical history, skin prick tests (SPT) with commercial and in-house extracts, prick-by-prick test, specific IgE measurements and challenge tests. PBS-soluble and insoluble extracts of both fig skin and pulp were examined for the presence of potential allergens by IgE immunoblotting.

Both patients showed OAS followed by respiratory symptoms when challenged with fig. They were negative in both specific IgE detection and SPT with commercial extracts of fig and many other plant materials, including F. benjamina and Hevea Brasiliensis, while grass and birch pollens gave positive results. Prick-by-prick tests and SPT with in-house extracts indicated that the fig skin had a much higher allergenicity than the pulp. Despite negative IgE detection by the CAP assay, immunoblotting experiments showed that potential fig allergens were PBS-soluble and present only in the skin of the fruit.

OAS to fig followed by respiratory symptoms can be present in patients not sensitised to weeping fig or having the latex-fruit syndrome. Different parts of the fig can have different allergenicities, the most important allergens being proteins related to the skin of the fruit. Improved commercial fig extracts to be used for the diagnosis of this type of allergy have to be developed.