Food allergy can occur in exclusively breastfed infants even though it is very rare. Some factors that cause low food allergy in exclusively breastfed infants are the protective effects of breast milk such as IgA antibodies and partially processed food proteins. The threshold dose of allergen reaching breast milk is generally too low to trigger an allergic reaction. Breast milk also contains microbiota that has an effect on the gastrointestinal immune system. Breast milk increases mucine production, which decreases intestinal permeability, thereby improving intestinal barrier function.

Infants who are exclusively breastfed still can show signs and symptoms of food allergy. This is thought to be due to maternal dietary macromolecules that are absorbed in the gut and transmitted in human milk. Cow's milk, egg, wheat and peanut allergens have been detected in human milk. Atopic dermatitis is the most common manifestation seen during the breastfeeding period, and is occasionally caused by food allergy. Immediate-type (e.g. IgE-mediated) allergic reactions, including hives and anaphylaxis, have occasionally been reported to occur through exposure to dietary proteins ingested in breast milk, and confirmed in physician-supervised oral challenge procedures. Gastrointestinal manifestations of food allergy, including abdominal pain/infantile colic and proctocolitis, and well-defined presentations, such as allergic eosinophilic esophagitis (EoE)-associated gastroenteritis and, rarely, food protein-induced enterocolitis syndrome (FPIES), have been described in exclusively breastfed infants.

After appropriate diagnostic process, management of food allergy in infants is to avoid food allergens completely. In infants who are exclusively breastfed, the mother must avoid the food allergen. Mothers should pay attention to substitutes for nutrients needed while avoiding these food allergens. 

Sometimes it is difficult to determine the foods that cause allergic reactions in non-IgE-mediated food reactions because there are no tests available. It is not recommended to do unguided multiple food elimination diet because it can interfere with maternal nutrition in addition to giving a psychological burden to mother, which results in failure of the breastfeeding process. In selecting the foods that need to be avoided, we must go through a detailed history and examination process. Food elimination is based on foods that empirically often cause allergic reactions.