Abstract Background: Exposure to infant milk formula (IMF) or cow's milk in the first year of life and its ‎association with susceptibility genes has attracted much attention in their possible role in inducing ‎autoimmune destruction of islet beta cells and Type 1 Diabetes (T1D).‎ Aim: To investigate the relationship between exclusivity and duration of breastfeeding and the ‎genetic basis of this disease in patients with TID.‎ Methods: The study included 24 diabetic children with TID matched with 21 controls. All the ‎children were exposed to detailed history of the disease process and anthropometry for weight, ‎height and body mass index. Blood samples were collected from all 45 cases for measuring HLA-‎DRB1 allelic polymorphism for the susceptible genes of HLA-DRB1 0301, 0302, 0401 and 0402 ‎by polymerase chain reaction sequence specific primer (PCR-SSP) done by genomic DNA ‎extraction using Genomic DNA purification kits.‎ Results: Allelic polymorphism for the susceptible genes of HLA-RB1 were shown to be higher in ‎the diabetic group compared to the control group especially for the 0302 and 0401 alleles at P<0.05, ‎but was not significant for HLA-RB1-0301 and 0402 at P>0.05. TID cases who were exposed to ‎IMF early in life exhibited earlier onset of the disease, more frequent episodes of DKA and ‎significantly higher BMI at P<0.05.‎ Conclusions: Exclusive breastfeeding in the first 6 months of life exerts protection against TID ‎most possibly by promoting complete maturation of gene expression. While exposure to other milks ‎early in life may exert gene modulatory effects and amplify allelic polymorphism increasing ‎susceptibility to the disease. ‎