Cows' milk allergy

Cows’ milk allergy, also known as cows’ milk protein allergy, is the most common food allergy in infants and is more frequently seen in formula-fed than breastfed babies

Cows’ milk allergy (CMA) is thought to affect between two and seven per cent of babies under one year of age, although the majority will grow out of it by the age of three years.


There are a number of different symptoms, which generally involve the skin and one or more other body system, including the gastrointestinal and respiratory systems. Symptoms may include:

  • Swelling of the face, hives, wheezing
  • Diarrhoea and vomiting
  • Constipation, bloating and abdominal pain
  • Colic.

Other symptoms can include eczema, rashes and breathing difficulties in severe cases. Between 50 and 60 per cent of babies with atopic eczema will also have an allergy to cows’ milk, causing their skin symptoms to worsen.


The first time a baby has cows’ milk (whether in an infant formula milk or if it passes through breast milk), their immune system reacts to the protein it contains as if it were a foreign substance. The next time the baby has cows’ milk, the antibodies produced will trigger the various allergy symptoms.

Protein or lactose

Babies can react to the cows’ milk protein that passes through breast milk or that is used to make infant formula milk, or they may have difficulty digesting lactose (a natural sugar found in milk). It is important to ascertain whether it is the protein or the lactose that is causing the problem.


If you think a baby may be allergic to cows’ milk, refer to a GP for a diagnosis. Total avoidance of cows’ milk protein is usually required, which may involve mothers of breastfed infants avoiding cows’ milk and dairy products, alongside taking appropriate supplements (e.g. calcium and vitamin D). The situation should be monitored using a food and symptom diary, with cows’ milk being periodically reintroduced at intervals under medical supervision. For formula-fed infants, a suitable formula will need to be found that is tolerated as a drink, and for use in cereals and cooking.

Cows’ milk allergy is thought to affect between two and seven per cent of babies under one year of age

Formula milks

The latest guidance advises using an extensively hydrolysed formula (EHF) such as Aptamil Pepti 1 or 2, which is still based on cows’ milk, although the proteins have been broken down to make them less allergenic. There are also amino acid-based formulas (AAFs) where the protein is made up of individual amino acids so that it does not trigger allergic reactions. AAFs are considerably more expensive, so are usually reserved for those with severe cows’ milk or multiple food allergies who cannot tolerate EHFs.

The Department of Health recommends that soya-based formula milks (e.g. SMA Wysoy Soya Infant Formula) are only given to babies on the advice of a GP or health visitor. This is because infants may also be allergic to soya protein and these formulas increase exposure to plant phytoestrogens while babies’ organ systems are immature and vulnerable. However, for some babies this may be all that they can tolerate. They can be used for babies who cannot tolerate the EHFs as they are more palatable, or for those who choose soya-based formula for lifestyle reasons, such as vegetarians and vegans.

N.B. Vegan diets are not recommended for babies.

Help for parents

Parents may require additional support and information, ideally from a dietitian, especially as their baby gets older and starts weaning onto solid foods. Knowing plenty of milk-free recipes will be helpful. There are also a number of dairy-free products available to buy now. The labels of all foods should be checked for their contents as milk can be present where it is not expected.

Clinical summary:

Food allergy is an adverse immune response and may be immunoglobulin-E (IgE; an antibody)-mediated or non-IgE-mediated (in which case T-cells are thought to be responsible), or both. IgE-mediated reactions are acute and often have a rapid onset, e.g. skin reactions, angioedema of the lips, tongue and palate, nausea and vomiting, respiratory symptoms (sneezing, rhinorrhoea, cough, wheezing or shortness of breath). Non-IgEmediated reactions tend to be delayed, e.g. itching, atopic eczema, GORD, changes in stools, tiredness and faltering growth.

According to NICE, diagnosis should be considered in a child whose symptoms do not adequately respond to treatment for atopic eczema, GORD or chronic GI problems including constipation, aided by taking an allergy-focused clinical history (e.g. personal and family history of atopy, symptom type, severity, duration and reproducibility, and dietary details). The child should also be assessed for physical signs of malnutrition or faltering growth, and signs of any allergy-related comorbidities.

Management of the allergy depends on whether or not IgE is thought to be responsible. If an IgEmediated reaction is believed to be the cause, a skin prick or blood test for specific IgE antibodies to the suspected food and co-allergens should be conducted. For non-IgE-mediated allergies, the suspected allergen should be eliminated from the diet for between two to six weeks and then reintroduced (under medical supervision).

If cows’ milk protein allergy is suspected, the mother should be provided with advice on food avoidance if she is breastfeeding, or information on the most appropriate formula or milk-substitute if formula-feeding. A referral to a dietitian may be required, as may signposting to support groups. Specialist care is recommended for individuals who experience faltering growth accompanied by GI symptoms that are thought to indicate a food allergy, have had one or more acute systemic or severe delayed reactions or have not responded to a single-allergen elimination diet, or if there is suspicion of multiple food allergies (even if test results are negative).


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