Molar-incisor hypomineralisation is a disturbance in dental development that involves first permanent molars as well as permanent incisors with a prevalence that ranges from 2.5% to 40%.The objective of this study was to investigate the effect of atopic diseases on the development of molar-incisor hypomineralisation.The study was based on the review of the medical records of a group of 102 children whose age was between eight and 12 years and 11 months and who had previously been diagnosed with MIH.An association (χ2, p≤0.05) has been found between molar-incisor hypomineralisation in children's mouths and the existence of: atopic dermatitis (OR=2.504; 1.54-4.05 CI 95%), food allergies (OR=2.171; 1.03-4.56 CI 95%), allergic rhinitis (OR=0.17; 0.02-1.27 CI 95%), and asthmatic bronchitis/asthma (OR=1.707; 1.05-2.76 CI 95%). When analyzing the pathologies by location, we found that atopic dermatitis, food allergies, allergic rhinitis and asthma were more frequent in children who had (p≤0.05) #12, #11, #21, #22, #36, #31, #41 and #42 affected.The association between molar-incisor hypomineralisation and the presence of atopic diseases in the first 36 months of life underlines the convenience of approaching this problem from a multidisciplinary perspective.