Key takeaways: Cow’s milk protein allergy (CMPA) affects a small percentage of babies. Signs range from hives and vomiting to blood in the stool and eczema. It’s diagnosed by removing cow’s milk protein and watching for improvement. Most babies outgrow it.
Cow’s milk protein allergy (CMPA) is the most common food allergy in infants, but it’s also often over-diagnosed. Understanding the signs and how it’s confirmed can help you get the right care.
What Is CMPA?
CMPA is an immune reaction to proteins in cow’s milk (casein and whey). It’s different from lactose intolerance, which is a problem digesting milk sugar and is rare in babies. Estimates suggest CMPA affects about 2 to 3 percent of infants or less, depending on how it’s defined.
Two Main Types
Immediate (IgE-mediated) reactions happen within minutes to 2 hours after exposure:
- Hives, swelling of the lips or face.
- Vomiting.
- Wheezing, coughing, or trouble breathing.
- Rarely, anaphylaxis.
Delayed (non-IgE-mediated) reactions happen hours to days later:
- Blood or mucus in the stool (allergic proctocolitis), often in an otherwise healthy, thriving baby.
- Vomiting, diarrhea, or constipation.
- Poor weight gain.
- Worsening eczema.
- Persistent fussiness alongside other symptoms.
FPIES (food protein-induced enterocolitis syndrome) is a less common delayed reaction causing repeated, severe vomiting 1 to 4 hours after eating, sometimes with lethargy and paleness.
Diagnosis
There’s no single perfect test for delayed CMPA. Diagnosis usually involves:
- A careful history and exam.
- Elimination: removing cow’s milk protein for 2 to 4 weeks to see if symptoms improve.
- Reintroduction: a planned return of cow’s milk to confirm symptoms come back, under your doctor’s guidance (except after severe reactions).
- For immediate reactions, an allergist may do skin prick or blood tests.
Formula Options
- Extensively hydrolyzed formula: the usual first choice. Proteins are broken down so most babies with CMPA tolerate it.
- Amino acid-based formula: for babies with severe reactions or who don’t improve with extensively hydrolyzed formula.
- Soy formula: an option for some babies over 6 months, but many babies with CMPA also react to soy.
- Partially hydrolyzed (“gentle”) formulas, goat’s milk, and plant milks are not appropriate for treating CMPA.
Breastfeeding With CMPA
Small amounts of cow’s milk protein from your diet can pass into breast milk. If your breastfed baby has symptoms, your doctor may recommend removing all dairy from your diet for 2 to 4 weeks. If symptoms improve, you may continue a dairy-free diet. If not, dairy can be reintroduced. Work with your provider or a dietitian to make sure you get enough calcium, vitamin D, and protein. Continuing to breastfeed is usually encouraged.
Outlook
Most babies outgrow CMPA. Many tolerate milk by age 1 to 3, and the majority by school age. Allergic proctocolitis often resolves by about 12 months. Your doctor or allergist will guide reintroduction, sometimes using a “milk ladder” that starts with baked milk.
Call 911 if your baby has trouble breathing, swelling of the face or tongue, repeated vomiting with lethargy, or becomes pale or limp. Call your baby’s doctor if your baby: has blood in the stool, hives, frequent vomiting, poor weight gain, or worsening eczema.
The Bottom Line
CMPA is real but less common than many people think. It’s diagnosed through elimination and reintroduction, treated with hydrolyzed formula or a dairy-free diet for breastfeeding parents, and usually outgrown.
Want more support for your baby’s first year? My book, From First Breath to First Birthday, is available on Amazon.
Sources
- Koletzko S, Niggemann B, Arato A, et al. Diagnostic approach and management of cow’s-milk protein allergy in infants and children: ESPGHAN GI Committee practical guidelines. J Pediatr Gastroenterol Nutr. 2012;55(2):221-229.
- Vandenplas Y, Broekaert I, Domellöf M, et al. An ESPGHAN position paper on the diagnosis, management, and prevention of cow’s milk allergy. J Pediatr Gastroenterol Nutr. 2024;78(2):386-413.
- Nowak-Węgrzyn A, Chehade M, Groetch ME, et al. International consensus guidelines for the diagnosis and management of food protein-induced enterocolitis syndrome. J Allergy Clin Immunol. 2017;139(4):1111-1126.
- Mennini M, Fiocchi AG, Cafarotti A, et al. Food protein-induced allergic proctocolitis in infants: literature review and proposal of a management protocol. World Allergy Organ J. 2020;13(10):100471.
- Meek JY, Noble L; Section on Breastfeeding. Policy statement: breastfeeding and the use of human milk. Pediatrics. 2022;150(1):e2022057988.
This article is for general education and is not a substitute for individualized medical advice. Always talk with your baby’s health care provider or your own provider about your specific situation. If you think your baby or you may have a medical emergency, call 911.
