According to the ‘Th1/Th2 paradigm’, children with type 1 diabetes mellitus (T1DM) should have a lower risk of developing allergic sensitization and, because of the involvement of insulin in modulating airway inflammation, different frequency or severity in allergy-related respiratory manifestations. This article aims at evaluating the frequency and type of allergic sensitization and its respiratory manifestation, asthma and/or rhinitis, in a group of pediatric patients with T1DM. Patients (112) with T1DM, 7.8-16.9 yr of age (63 males and 49 females) were evaluated. Skin prick test (SPT) reactivity to the most common classes of aeroallergens were performed and compared with data obtained in 709 school-aged children. The frequency of sensitization was not different in the T1DM and in the control subjects (43.7% and 40.8%, respectively; p = 0.55), with similar proportions of individuals sensitized to one allergen (32.7% and 38.1%, respectively; p = 0.47). In both groups, sensitization to house dust mite allergens was the most frequently detected (69.4% and 65.4%, respectively; p = 0.59), with a higher proportions of individuals sensitized to Graminae (+Cynodon dactylon; p < 0.0001) and a lower, but weakly significant, proportion sensitized to Parietaria (p = 0.03) in the T1DM group, as compared with controls. No differences were found between T1DM and control groups in the proportion of individuals reporting rhinitis (26.8% and 29.2%; p = 0.60). However, comparing separately sensitized and non-sensitized subjects, a lower proportion of rhinitis subjects was detected in the non-sensitized T1DM patients, when compared with the non-sensitized control subjects (p = 0.01). In addition, no differences were detected between T1DM and control groups in frequency of symptoms related to ‘lifetime asthma’, i.e., asthma episodes during life (14.3% and 16.5%, respectively: p = 0.55), also when sensitized and non-sensitized subjects were evaluated separately (p = 0.12 and p = 1.00, respectively). However, no T1DM patient had ‘actual asthma’, i.e., asthma episodes in the last year, vs. 5.8% of the individuals in the control group (p = 0.009), the difference being mostly ascribed to sensitized subjects (p = 0.012). Finally, out of the 16 T1DM patients with ‘lifetime asthma’, 15 had mild intermittent disease and only one mild persistent disease. T1DM does not seem to play a downregulating role on the development of allergic sensitization to aeroallergens, but may lower the frequency or the severity of its clinical manifestations at respiratory level.