Introduction: Patients with birch pollen allergy frequently develop hypersensitivity reactions to certain foods, e.g. apples, celery and carrots. Mostly, it is caused by cross-reactivity between these allergens. Diagnosis of this allergy became possible due to using methods, such as e.g. immunoblotting.

Matherial and methods: Nineteen patients with birch pollinosis suffering after eating apple, celery, carrot were included to the study. Skin prick tests were performed and serum IgE levels (total and specific) were determined in all individuals. Immunoblotting was performed in all  patients.

Results: Sera of only three patients revealed the strong reaction against birch pollen protein with a molecular weight 17–18 kDa corresponding to the main birch allergen Bet v 1. Serum of only one patient revealed the presence of antibodies cross-reacting with apple, celery and carrot protein with the same molecular weight, which may indicate main allergens of these foods – Mal d 1, Api g 1 and Dau c 1.

Conclusions: Immunoblotting, instead of its limitations, is helpful diagnostic method to confirm presence of cross allergy.