Difference between lactose intolerance and cow’s milk protein allergy (CMPA)

Difference between lactose intolerance and cow’s milk protein allergy (CMPA)

Frequently, the differences between lactose intolerance and CMPA, which stands for cow’s milk protein allergy, are not well distinguished. This happens not only to families but also to healthcare professionals. A food allergy and food intolerance are both adverse reactions to the consumption of certain foods. Differentiating the symptoms, causes, and treatment is key to guiding families in case their infants suffer from any of these pathologies.

Food allergy is a reaction of the immune system that causes repeated symptoms after exposure to a food that is usually well tolerated by healthy individuals. Cow’s milk protein allergy (CMPA) is the most common type of food allergy in the first year of life and usually involves the immune system.

It shows through digestive symptoms, mainly of early or late onset after contact with the food. In the case of exclusive breastfeeding, when the mother consumes food containing these proteins, they reach the breastmilk in the form of small sequences of amino acids (AA, molecules that combine to form proteins). The passage of these molecules can cause hypersensitivity reactions in the breastfed baby, so exclusions in the mother’s diet are necessary to avoid them.

Symptomatology is usually diverse and non-specific, although predominantly digestive, symptoms range from severe nutritional impairment to correct weight gain with little systemic impact:

  • Generally being unwell following a feed
  • Gastrointestinal reflux
  • Presence of blood and/or mucus in stools
  • Vomiting
  • Diarrhea or constipation
  • Atopy
  • Impaired physical development (poor weight and height gain).

In case of suspected allergy and in order to confirm it, the breastfeeding mother should follow a diet free of cow’s milk protein and foods containing traces of these proteins to aim for a resolution of the symptoms in the breastfed baby (there is no need to stop breastfeeding). Depending on the degree of allergy and the infant’s situation, the improvement and resolution of the symptoms are variable, ranging from 1-5 days in acute forms up to 2-4 weeks in case of infants with diarrhea, constipation, or nutritional status affectation. After this period, a provocation test (reintroducing cow’s milk protein into the maternal diet) is required to see if symptoms reappear.

Intolerance is described as the inability of the organism to assimilate a certain food or one of its components correctly. They are usually caused by non-protein food components, and the immune system is not involved.

In relation to breastfeeding, lactose is a carbohydrate naturally present in the milk of mammals. The exclusion of dairy and related products in the maternal diet would not be the strategy to choose in case of digestive symptoms of a baby because the presence of lactose does not depend on the mother’s diet. However, in certain circumstances, infants may suffer a temporary lactose intolerance, such as acute gastroenteritis (stomach bug).

If this is the case, the first option is to maintain unrestricted breastfeeding according to the infant’s needs and, in the case of mixed feeding or formula feeding, to make use of lactose-free formulas until the baby has recovered from the condition that caused the problem.



Mehaudy R, Jáuregui MB, Vinderola G, Guzmán L, Martínez J, Orsi M, Parisi C. Cow’s milk protein allergy; new knowledge from a multidisciplinary perspective. Arch Argent Pediatr. 2022 Jun;120(3):200-206. English, Spanish. doi: 10.5546/aap.2022.eng.200. PMID: 35533123.

Espín Jaime B, Díaz Martín JJ, Blesa Baviera LC, Claver Monzón A, Hernández Hernández A, García Burriel JI, et al. Alergia a las proteínas de leche de vaca: do- cumento de consenso de la Sociedad Española de Gastroenterología, Hepatología y Nutrición Pediátri- ca (SEGHNP), la Asociación Española de Pediatría de Atención Primaria (AEPAP), la Sociedad Española de Pediatría Extrahospitalaria y de Atención Primaria (SEPEAP) y la Sociedad Española de Inmunología Clínica, Alergología y Asma Pediátrica (SEICAP). An Pediatr (Barc). 2019;90:193.e1-193.e11.

García Mérida MJ, Espín Jaime B. Alergia a las proteínas de la leche de vaca no mediada por IgE. En: AEPap (ed.). Congreso de Actualización Pediatría 2020. Madrid: Lúa Ediciones 3.0; 2020. p. 239-245.




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