Early exposure to potentially allergenic foods during the complementary feeding period, when the infant begins to consume foods other than breast milk, may reduce the risk of food allergy by inducing oral tolerance. Cow's milk, egg, peanut and fish are among the potentially allergenic foods included in guidelines and recommendations. There is also a recommendation for the introduction of gluten in complementary feeding. Nowadays, the timing of the introduction of potentially allergenic foods has changed in parallel with the increasing prevalence of food allergy. There are various guidelines regarding the timing of introduction of these foods, especially in infants at high risk of allergy. According to these guidelines, the introduction of egg and peanut in complementary feeding at 6 months of age reduces the risk of food allergy. However, cow's milk and fish have no significant effect on the risk of allergy. Among cereals, foods made from wheat are most commonly consumed. Early or late introduction of gluten protein in wheat does not affect the prevalence of celiac disease in childhood. Recommendations on this subject should be made taking into account the negative consequences that may be caused by the food recommended for later consumption in the complementary feeding.