Breastfeeding and Cow's Milk Allergy

Breast feeding is the best feeding option for all infants, including those with CMA^1,3. In some cases (~0.5%) the infant may react to cow’s milk protein from the maternal diet that are transferred through the breast milk². In such cases, the mother should be supported to continue breast feeding and advised to remove cow’s milk from her own diet. Vitamin D and Calcium supplementation should be advised for these mothers and alternative ‘milks’ that are fortified should be recommended.⁴

Below we will discuss the appropriate management of breastfed infants with CMA.

It is important to remember that not all breastfed babies will react to the cow’s milk proteins, specifically beta-lactoglobulins, in breast milk³. 

The amount of milk proteins present in breast milk is 100,000 times lower than in cow’s milk. Some infants may only react when they ingest cow’s milk proteins in their own diet either through a standard infant formula or on weaning with solids containing ‘dairy’.^1,3

Soya and egg proteins can also be found in breast milk and can lead to similar reactions.⁴ These are less common but are important to consider if CMA is suspected and there is no clear improvement, or limited improvement on the milk free diet.  Careful management of the mother’s diet is needed with any dietary exclusion³.

Common symptoms seen in breastfed babies are mild or moderate and may include eczema and/or diarrhoea, which can sometimes contain blood and mucous. Severe reactions are rare, and it is thought that this is due to breast milk containing secretory immunoglobulin A which is unique to breast milk and helps protect the baby from potential allergens being penetrated through the intestinal wall. Symptoms usually present soon after breastfeeding commences or when a cow’s milk formula and/or weaning foods containing dairy are given⁵.

Dietary elimination

If there is suspicion that an infant is reacting to the cow’s milk proteins in breastmilk, then strict maternal dietary elimination is indicated for 2 – 4 weeks³.

Taking a diet history can help direct the nutrition advice by finding suitable milk-free alternatives to ensure the dietary prescription of a milk free diet is personalised.  A fortified plant based ‘milk’ and plant based yoghurts are good options to include in the diet while dairy is being eliminated³ and a wide range is now fortunately available in Irish supermarkets.

Confirming the diagnosis

After the 2- 4 week maternal elimination period it is crucial to confirm the diagnosis to avoid unnecessary dietary eliminations from the mother’s diet³.

Cow’s milk and cow’s milk containing foods should be slowly reintroduced into the mother’s diet over a one-week period³. 

It is helpful to use a food symptom diary to track any changes in the infant.  

If any symptoms return, the reintroduction of cow’s milk into the mother’s diet should stop and a milk free diet should resume.  A milk free diet is then recommended until the baby is 9 – 12 months of age and for at least 6 months.  Milk free weaning will need to be discussed³. 

If there has been no change during the elimination period and reintroduction, then cow’s milk and cow’s milk products can be returned into the mother’s diet, and a diagnosis of CMA is unlikely³.

A complete soya exclusion may need to be reviewed and egg if there is ongoing suspicion of a food allergy, but this should be discussed with the team with a clear treatment plan in place³.

If a maternal milk free diet is required, the mother will need advice on which foods to avoid including both obvious sources of milk but also products which contain hidden sources of milk protein. These can include:

• Margarine
• Cakes
• Biscuits
• Some breakfast cereals
• Bread
• Pastry
• Ready-made meals or sauces
• Instant custard, potato, or soup.

Lactose-free milk, cheese and yogurts are not suitable as they still contain cow’s milk protein.

It is important to identify a plant based ‘milk’ that contains both calcium and iodine as well as discuss examples of milk free spreads, yoghurts, and cheese.  It is worth considering avoiding replacement with soya products during the trial as the proteins are similar to cow’s milk proteins and some babies may cross-react to them too. A small amount of soya found in certain brands of bread is usually not an issue, but this should be discussed with the team.

Providing guidance on amounts of milk alternatives, yogurt, and cheese to meet calcium and iodine requirements is important. There is usually around 120mg calcium in 100ml milk alternative or 100g dairy free yogurt.

Many of the cheese alternatives readily available are not fortified with calcium and some only contain small amounts and so it is important to highlight this to avoid confusion with calcium requirements.

It is helpful to discuss meals and how to use dairy alternatives to replace the dairy components of recipes. This is to enable family meals to be made and avoid separate meals being prepared that will increase workload and time for the family whilst on the elimination diet. Additional support from family and friends can be helpful during this time.

Due to increased energy requirements whilst breastfeeding, it is useful to provide examples of suitable snacks.

It is important to show families how to check if foods are suitable by talking them through how to read the ingredients list and being able to identify if they are milk free.

Eating out can be challenging and it is recommended to phone ahead and check that they can accommodate a milk-free diet highlighting caution on using soya as a replacement to milk.

The Food Safety Authority of Ireland (FSAI) recommends that all breastfed babies should be given a daily supplement containing 5 micrograms (µg) of vitamin D from birth to 1 year of age.

If the infant with CMA is being mixed breastfed and formula fed, the FSAI recommend that they should not be given a daily vitamin D supplement if they are having more than 300ml (about 10 fluid ounces) of their hypoallergenic formula per day.

In Ireland, the FSAI (2024) do not make specific recommendations for Vitamin D supplementation for breastfeeding mothers, but instead they should follow the advice for all adults of taking a 15µg vitamin D supplement per day during the extended winter months (from Halloween to St Patrick’s day).