Kiwi fruit allergy: a new birch pollen-associated food allergy.

BACKGROUND

To determine the cross-reacting antigens of kiwi fruit and other foods and pollen, we investigated 22 patients allergic to kiwi fruit: 10 with severe systemic reactions and 12 with localized symptoms confined to oral and pharyngeal mucosa (oral allergy syndrome). Seven patients with birch pollen allergy who tolerated kiwi fruit were included as a control group.

METHODS

All patients were evaluated by skin testing and RAST; three patients were evaluated by RAST inhibition assays.

RESULTS

Prick tests showed positive reactions to kiwi fruit in all patients, whereas specific IgE to kiwi fruit could be demonstrated only in patients with generalized severe symptoms. Surprisingly, all 22 patients with clinical kiwi allergy showed positive prick test results and elevated IgE to birch pollen. Clinically, all complained of rhinitis during birch pollen season. Many patients showed sensitization to grass and mugwort pollen. Also, food allergy was found to be associated with kiwi allergy: we found strong reactions to apple and hazelnut; moderate reactions to carrot, potato, and avocado; and weak reactions to wheat and rye flour, pineapple and papaya, and their enzymes bromelain and papain. RAST inhibition studies revealed cross-reacting antigens between birch pollen and kiwi fruit. Interestingly, patients with birch pollen allergy without clinical signs of kiwi allergy had positive prick test reactions to kiwi. Patients with kiwi allergy showed higher concentrations to birch pollen IgE compared with patients with isolated birch pollen allergy.

CONCLUSIONS

Our results indicate that kiwi allergy is a new manifestation of birch pollen-associated food allergy and is mediated by cross-reacting antigens in the kiwi fruit. Kiwi allergy can be expected in patients with birch pollen allergy exhibiting high levels of IgE to birch pollen.