BACKGROUND: Conflicting results have been obtained when analyzing the relationship between complementary feeding (CF) practices and allergic diseases in childhood. This study aims to further explore the association between allergic diseases in early childhood (10.1016/j.jaci.2012.02.036) and the age at CF introduction (10.1016/S0140-6736(15)00149-X), food diversity in the first year of life (10.1016/j.ijporl.2019.109759) and the delayed introduction of major allergenic foods. METHODS: This analysis focused on 6662 children from the French nationwide ELFE cohort. Data on feeding practices were collected monthly from 3 to 10 months old. Their age at CF introduction was calculated alongside a diversity score, and the number of major allergenic foods (out of eggs, fish, wheat, and dairy products) not introduced at 8 and 10 months. Their associations with parent-reported allergy-related health events between 1 and 5.5 years were assessed using logistic regressions adjusted for confounding factors. A sensitivity analysis excluding early allergic cases (occurring between 2 months and 1 or 2 years) was conducted. RESULTS: Late CF (>6 months) was related to a higher risk of food allergy (OR [95% CI] = 1.35 [1.02; 1.78]), a low diversity score at 8 months to a higher risk of asthma (OR [95% CI] = 1.22 [1.01; 1.48]), and two allergenic foods or more not being introduced at 10 months to a higher risk of rhinoconjunctivitis (OR [95% CI] = 1.20 [1.00; 1.44]) and food allergy (OR [95% CI] = 2.46 [1.77; 3.42]). Only this last association remained significant after the exclusion of early cases. CONCLUSION: The delayed introduction of major allergenic foods is related to a higher risk of food allergy, which supports the updated guidelines for allergy prevention.