Allergic diseases are highly prevalent, and they can exert a significant influence on the patients’ physical and mental well-being, thus affecting the quality of their lives and society as a whole. The aim of this study was to evaluate parental knowledge about allergens, allergy symptoms, and treatment of allergies, and to identify problems with adherence to an elimination diet and the underlying difficulties. Twelve kindergartens and the parents of 1350 preschoolers took part in the first stage of the study. In a screening trial, allergies were diagnosed in 197 children, and their parents participated in the second stage of the study. The child’s age at the onset of the first symptoms was significantly correlated with allergy type. Age was significantly correlated with selected symptoms of an allergic reaction, and skin allergies were more prevalent in younger children. Erythema, skin reddening, and urticaria occurred more frequently in children aged 3–4 years (OR 1.45; 95%CI 1.24–1.77, p < 0.05) and were diagnosed in skin tests (OR 1.36; 95%CI 1.22–1.59, p < 0.05). Allergies to numerous food items were associated with a long-term elimination diet (OR 1.89; 95%CI 1.33–2.19, p < 0.01), as well as problems with preparing safe meals, shopping for food, or dietary adherence when eating out. According to the respondents, lack of support from other family members and compliance with dietary restrictions in kindergartens and when eating out posed the greatest barriers to dietary adherence. Parents do not have sufficient knowledge about environmental allergens and effective strategies for coping with acute allergic reactions, including anaphylactic shock. Children with diagnosed food allergies should enjoy a similar quality of life to their healthy peers, which is why the parents should be educated about diet therapy, duration of treatment, and safe food substitutes.