According to literature, approximately 20%-70% of patients sensitized to pollen allergens experience oral allergy syndrome (OAS) symptoms after eating raw fruits and vegetables. There is no standard treatment established for OAS except avoiding implicated food. However, in patients with airborne pollen allergy treated with specific immunotherapy (SIT), an improvement of OAS symptoms has been reported in 30% to even 84% of individuals examined. The aim of the present study was to evaluate the prevalence of OAS symptoms in patients with various manifestations of pollen airborne allergy (atopic dermatitis (AD), asthma, allergic rhinitis) treated with subcutaneous type of SIT. In addition, the most common patterns of cross-reactivity in OAS were analyzed and correlations between OAS symptoms and patient age, type of sensitizing pollen allergens and atopy manifestations investigated. Also, the relationship between SIT duration and clinical improvement of both OAS symptoms and pollen allergy symptoms was analyzed. The study included 57 patients with airborne allergy treated with allergen vaccination (60% male and 40% female). Allergic rhinitis was diagnosed in 71%, AD in 19%, AD and asthma in 4%, allergic rhinitis and asthma in 4%, and both AD and allergic rhinitis in 2% of study patients. Twenty-eight percent of study patients complained of overt symptoms of OAS (22% of allergic rhinitis patients and 27% of AD patients); 69% of the subjects presenting with OAS showed polyvalent airborne allergy to pollens and 31% were sensitized to only one group of pollen allergens (mostly grass pollens, tree pollens and mugwort pollens). There was no statistically significant correlation between the presence of OAS symptoms and patient diagnosis, patient age and type of allergen vaccination used. According to patients' opinion, SIT significantly improved oral symptoms in 50% of study patients, 44% reported no impact of SIT on OAS symptoms and 6% of patients observed worsening of OAS symptoms after unintentional ingestion of implicated food during the course of SIT. The study revealed OAS as a significant problem in patients sensitized to various pollen allergens. The results on OAS prevalence in atopic subjects (28%) were consistent with some literature data. There was clear association between OAS and polyvalent airborne allergy (69%). Cross-reactivity patterns were typical (for example, tree pollen allergy - intolerance of apples, carrots and potatoes; grass pollen allergy - intolerance of kiwi fruit and tomatoes). Questionnaire analysis indicated that subcutaneous SIT significantly alleviated OAS symptoms associated with ingestion of the responsible fruit and vegetables in half of study subjects. Further evaluation of the duration/persistence and stability of the phenomenon is planned for the future.