How does cow’s milk allergy impact infants?

The symptoms of cow’s milk allergy are wide-ranging and non-specific – meaning they are also found in many other conditions. Typically, symptoms affect the digestive and respiratory systems and the skin2-5. Many parents wait months for their baby to be diagnosed with cow’s milk allergy (also known as cow’s milk protein allergy)1. The process can involve many doctor visits and can be distressing for both the parents and the child1


Cow’s milk allergy symptoms

Symptoms can happen right after feeding or be delayed by a few hours to several days6,7. If your child often has any of the symptoms below, it is important that you discuss them with your doctor. It is also important to remember that many other conditions can result in these symptoms.

Digestive symptoms

Up to 60% of infants with cow’s milk allergy have gastrointestinal4 symptoms such as:

  • Frequent vomiting after feeds5

Many babies vomit, especially after feeding. However, if a baby is frequently vomiting after feeds, it may be time to see the doctor as it could point to gastroesophageal reflux disease (GERD) and/or cow’s milk allergy5,7

  • Reflux or ‘spitting-up’

Reflux is common in infants younger than one year. In almost half of infants, reflux may be linked to cow’s milk allergy7. If your baby is having frequent reflux and/or is spitting-up a lot, discuss this with your doctor.

  • Persistent diarrhea or constipation5

Diarrhea (multiple loose or liquid stools, several times a day) is a common digestive symptom in infants with cow’s milk allergy. While constipation is less common than diarrhea, it could also be a sign of cow’s milk allergy.

  • Blood and/or mucus in the stool5

Blood resulting from irritation in the gut can also be a sign of cow’s milk allergy in infants. 

Sticky mucus in their stools could resemble the mucus you see when you have a cold or runny nose. A little bit can be normal, but if you see a lot of mucus in your baby’s stool or it lasts a while, it is important that you let your doctor know about it.

  • Persistent gassiness

Gassiness is caused by too much air in the stomach or intestines and leads to discomfort. An excessively gassy baby may appear fussy, cranky or colicky. All babies have some degree of gas, but when it happens with several other symptoms, it may indicate an allergic reaction8

Skin-related symptoms

Up to 70% of infants with cow’s milk allergy have symptoms that affect their skin4.

  • Unexplained skin rashes/ hives6

Cow’s milk allergy-related rashes often appear on the face but can appear anywhere on the body. They tend to be very itchy and uncomfortable and may be worse after feeding.


Respiratory symptoms5

Up to 30% of babies with cow’s milk allergy have either mild or severe respiratory symptoms4

  • Breathing difficulties

Mild respiratory symptoms are similar to those of the common cold, including runny nose, sneezing and congestion. More severe symptoms can include shortness of breath or difficulty breathing and wheezing6. Seek immediate medical assistance for any serious respiratory issues.

General symptoms

  • Excess fussiness, colic or sleeplessness6

Crying continuously and inconsolably for long periods – called ‘colic’ – is unusual. It can mean abdominal pain or be due to reflux, rash or other factors. Talk to your doctor if your baby cries for 3+ hours in a day, for 3+ days in a week, for over 3 weeks. 

  • Little or no weight gain6

Sometimes slow weight gain may lead to a diagnosis of ‘Failure to Thrive’, which is one of the symptoms of cow’s milk allergy. 

What to expect when your doctor is investigating the possibility of cow’s milk allergy

Diagnosis will take into account your child’s medical history, symptoms and may include a variety of allergy tests. 

Diagnosing cow’s milk allergy can take time, particularly if your child has a delayed allergic reaction to cow’s milk protein. But there are things you can do to help your doctor confirm or eliminate cow’s milk allergy as the cause of your child’s symptoms.


Symptom tracking

Your doctor is likely to ask a lot of questions around the details of your child’s symptoms. Keep a diary of when they feed and of any symptoms that occur after. Be sure to note down the time of feeding and when their symptoms happen, as well as for how long (minutes, hours, days). If you are breastfeeding, this diary should also keep record of everything you eat and drink. Aim to track your child’s food intake and symptoms for at least a week before seeing your doctor.

Diagnostic tests

Various tests are used to help diagnose food allergy. The most suitable allergy tests that your healthcare professional will undertake, will depend on the type of allergy your baby may have: IgE or non-IgE-mediated5,6.

Immunoglobulin E (IgE) is an antibody, a protein produced by the immune system to fight against a pathogen – or what it thinks is a pathogen (in the case of cow’s milk allergy, it will try to fight against the protein in cow’s milk). When the body detects the cow’s milk protein, specific cow’s milk protein antibodies travel to cells that release the chemicals that cause the allergy symptoms. 

Skin prick or blood tests are used for immediate allergic reactions (known as IgE mediated reactions). Elimination diets or food challenges may be used under the supervision of a qualified healthcare professional when your baby has delayed reactions (or non-IgE mediated reactions), because skin prick or blood tests are less effective for this type of allergy.

  • Skin prick test 
    Small drops of cow’s milk are placed on the child’s forearm. A small prick is made through each drop into the skin. If the child’s skin becomes red and itchy, it usually means that he or she is allergic.

  • Blood test

A blood sample is screened for IgE antibodies, which are often higher in children with allergies.

  • Elimination diet or food challenge

Under the guidance of a doctor and/or dietician, foods that may be causing an allergy are removed from baby’s diet for 2-6 weeks at a time, and then slowly put back to confirm suspected diagnosis. Reintroducing a food that is confirmed to cause an allergy after a period of time is known as a ‘food challenge’. This should only be done under medical supervision.

Preparing to see a doctor: what questions might they ask if they are considering a diagnosis of cow’s milk allergy:

  • Think about your child’s medical history and their recent symptoms. When did they start? When do they tend to happen? How often? Are they always the same?

  • Is there a family history of allergies, including asthma and eczema?

  • It may help your doctor to bring your symptom diary to your appointment 

  • Consider taking photos of your baby’s rashes/soiled nappies to show your doctor

  • Plan and draft a list of questions to ask your doctor 

  1. Sladkevicius E, Nagy E, Lack G, et al. J Med Econ 2010; 13(1): 119-128.
  2. Høst A. & Halken S. Allergy 1990; 45: 587-596.
  3. Meyer R et al. Current Allergy & Clinical Immunology 2012: Vol 25.
  4. Høst A. Ann Allergy Asthma Immunol 2002;89:33-37.
  5. Koletzko S, Niggemann B, Arato A, et al. J Pediatr Gastroenterol Nutr 2012; 55(2):221-229.
  6. Fiocchi A, Brozek J, Schunemann H, et al. Pediatr Allergy Immunol 2010;21:1-125.
  7. Salvatore S, Vandenplas Y. Pediatrics. 2002 Nov;110(5):972-84. doi: 10.1542/peds.110.5.972. PMID: 12415039.
  8. Venter C, Brown T, Meyer R, et al. Clin Transl Allergy. 2017 Aug 23;7:26. doi: 10.1186/s13601-017-0162-y. Erratum in: Clin Transl Allergy. 2018 Jan 25;8:4. PMID: 28852472; PMCID: PMC5567723.

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