What should I do if my baby is allergic to cow's milk protein?

Cow's milk is usually the first foreign protein in the diet of newborns. Cow's milk protein allergy (CMPA) is the most common food allergy disease in newborns. It is an immune response of the body to some protein molecules in milk, which can be mediated by IgE, non-IgE, or a mixture of both.

The incidence of CMPA is affected by regional differences and diagnostic criteria, ranging from 0.5% to 4.9%. The prevalence of CMPA in breastfed infants is approximately 0.5%. The reported incidence of CMPA in infants aged 0 to 2 years in my country is 0.83% to 3.5%. The true prevalence of CMPA remains controversial because its subjective perception is much higher than the actual prevalence of confirmed CMPA. Epidemiological studies have shown that the incidence and prevalence of allergic diseases have increased in the past few decades, which may be due to complex environmental, lifestyle and dietary changes.

Symptoms and diagnosis of CMPA

Neonatal CMPA is mainly non-IgE-mediated, with diverse and nonspecific clinical manifestations, often with bloody stools, vomiting, abdominal distension, diarrhea and other symptoms, usually occurring 2 hours after ingestion of allergens, generally 6-72 hours, which is a delayed allergic reaction. Clinical symptoms are diverse, often involving multiple systems, and can manifest as food protein-induced allergic proctocolitis, food protein-induced enterocolitis syndrome, food protein-induced enteropathy and Heiner syndrome. IgE-mediated CMPA is extremely rare in the neonatal period, with only individual case reports, manifested as urticaria and anaphylactic shock; IgE and (or) non-IgE-mediated CMPA only has atopic dermatitis in the neonatal period, which can manifest as non-eczematous manifestations, independent eczematous manifestations and mixed manifestations and is not limited to skin symptoms. Given that the digestive and immune systems of premature infants are not yet fully developed, in most cases, premature infants develop CMPA later, with more complex symptoms, more severe conditions, and are more susceptible to food protein-induced enterocolitis syndrome than full-term infants.

The diagnosis of CMPA in the neonatal period mainly relies on comprehensive analysis of high-risk factors for allergies, the relationship between clinical symptoms and food intake, the results of diagnostic avoidance tests, and the exclusion of other related diseases.

Dietary management of neonates with CMPA

1. When a breastfed newborn develops cow's milk protein allergy, it is recommended to continue breastfeeding, and the mother should strictly avoid foods containing milk and supplement with calcium and vitamin D preparations. If severe allergic symptoms occur, choose amino acid formula (AAF) or extensively hydrolyzed formula (eHF) for feeding.

For newborns with CMPA, continued breastfeeding should be encouraged, and mothers should avoid foods containing milk protein for 2 to 4 weeks. If mixed feeding is required for various reasons and it is impossible to completely breastfeed, it is recommended that CMPA children with mild clinical symptoms can choose PHF or eHF feeding. However, when the child has the following conditions, breastfeeding should be suspended and AAF should be selected for replacement feeding. In the case of long-term avoidance of the mother, it is recommended that the mother supplement calcium and vitamin D preparations at the same time.

2. When formula-fed newborns develop cow's milk protein allergy, eHF or AAF feeding is recommended.

When formula-fed newborns develop CMPA, international guidelines recommend that eHF replacement feeding be the first choice for infants with mild to moderate clinical manifestations. However, in the following situations, switching to AAF feeding may be considered: (1) eHF treatment is intolerant and symptoms do not improve after 2 to 4 weeks; (2) the child develops severe allergic symptoms, such as severe atopic dermatitis, allergic enteritis combined with growth retardation and/or hypoproteinemia and/or severe anemia, eosinophilic esophagitis, etc.; (3) the mother and family are extremely anxious and cannot accept any potential allergic risks.

Prevention measures for CMPA in newborns

Breast milk proteins are homologous proteins, and contain a small amount of food-specific antigens from the mother, such as ovalbumin, β-lactoglobulin, gliadin, and peanuts, which can properly stimulate the baby's immune system, promote immune development and immune tolerance, and prevent allergies. In addition, the rich oligosaccharides, secretory IgA, cytokines, and probiotics in breast milk can help reduce the risk of food allergies in infants.

Evidence suggests that exposure to cow's milk formula in the first 3 days of life increases the risk of CMPA in breastfed newborns. Therefore, avoiding temporary supplementation with cow's milk formula in the early postnatal period may substantially reduce the risk of CMPA in early childhood. Exposure to cow's milk in the first few days of life in breastfed infants may significantly increase the risk of CMPA. Therefore, breastfeeding in the neonatal period should be encouraged and the introduction of cow's milk formula in the early postnatal period should be avoided to reduce the risk of allergy.

In addition, it is not recommended to restrict the mother's diet of milk and its products during pregnancy and lactation to prevent CMPA; it is not recommended to use pHF to prevent CMPA in breastfed newborns. When breastfeeding is not possible or breast milk is insufficient, it is not recommended to use pHF or eHF to reduce the risk of CMPA in newborns at high risk of allergies; there is insufficient evidence to show that supplementation with probiotics, prebiotics or synbiotics, long-chain polyunsaturated fatty acids, and vitamin D can prevent CMPA.

Note: The content of this article refers to the "Expert Consensus on Diagnosis and Management of Cow's Milk Protein Allergy in Newborns (2023)" published in the 1st issue of the "Chinese Journal of Pediatrics" in 2024, developed by the Neonatology Group of the Pediatric Branch of the Chinese Medical Association and the Editorial Committee of the Chinese Journal of Pediatrics.