Background Many children encounter unusual or “exaggerated” reactions such as large local, atypical or systemic reactions after mosquito bites. Objective The aim of this study was to document the clinical features of children with mosquito allergy and investigate the possible associations between demographic features and type of reactions in this population. Methods Children with large local or unusual reactions after mosquito bites who attended to our outpatient pediatric allergy department were enrolled in the study along with control subjects. Results A total of 180 children (94 with mosquito allergy and 86 age and sex-matched control subjects) with a median age of 6.8 years (IQR 5.5–9.3) were enrolled. Atopy (35.1% vs. 11.6%, p < 0.001) and grass pollen sensitization (28.7% vs. 8.1%, p < 0.001) were significantly more frequent in children with mosquito allergy. Skin prick test with mosquito allergen was positive in only 6 children (6,4%). Grass pollen sensitization was most common in children (28.7%) followed by sensitization to house dust mite (9.6%). 30 children (31.9%) had an accompanying atopic disease such as allergic rhinitis, asthma or atopic dermatitis. Bullae were significantly more frequent in children with asthma (41.7% vs.15.9, p = 0.034). The median duration of symptoms after onset were significantly longer in patients with ecchymosis, with immediate wheals and in children whose symptoms start in 20 min to 4 hours after mosquito bites. Conclusion There is an association between unusual, large local or exaggerated reactions after mosquito bites and allergic diseases in children. The severity of reactions increases with age and particularly in children with atopic background.