Breastfeeding an Infant with Cow's Milk Allergy (CMA): A Guide for Parents & Carers  

CMA is the most common food allergy in infancy. CMA is an immune‑mediated reaction to proteins in cow’s milk, such as casein and whey proteins.¹ It is much less common in exclusively breastfed/chestfed infants but can occur as a small amount of the protein can be transferred via breast milk (human milk).

Symptoms can overlap with normal infant behaviour, making an appropriate diagnosis difficult.^2,3 CMA can look different from one baby to another, depending on how their body reacts.

There are two main types:

• IgE-mediated CMA: Symptoms occur quickly (minutes to 2 hours) and may include hives, swelling, or breathing difficulties
• Non-IgE-mediated CMA: Symptoms are delayed (hours to days) and typically involve the gut or skin (e.g. reflux, loose stools, eczema)

In breastfed/chestfed infants, non-IgE-mediated CMA is more common, making diagnosis more challenging.⁴ Most babies outgrow CMA with many tolerating milk again by 2–3 years of age.⁵ CMA should not be confused with lactose intolerance, which is rare in infants; CMA is an immune reaction to milk protein, while lactose intolerance is difficulty digesting milk sugar. Read more here.

All the CMA symptoms, particularly those of non-IgE mediated allergy, are also very common in babies who do not have a milk allergy, which makes diagnosis difficult. Symptoms such as colic, reflux and being unsettled may simply reflect normal stages of a baby’s development and will improve as they get older. Symptoms can range from very mild to severe and may affect different body systems. Mild symptoms may not need any changes to the mother (feeding parent), or baby’s diet at all. However, if you are concerned, seek medical advice early. Getting the right support can help improve symptoms and reassure you as a parent. 

CMA is more likely to be considered when symptoms occur in more than one body system (for example, skin, gastrointestinal or respiratory symptoms), or when symptoms do not improve despite appropriate standard management.

Step 1: Healthcare Professional assessment

A healthcare professional (GP, dietitian, health visitor or nurse) will ask a number of questions including:

• Type and timing of symptoms
• Feeding history
• Family history of allergy⁶

All babies with a likely or confirmed milk allergy should be referred to a dietitian for ongoing advice and support. You can ask for a referral if this has not been done. Depending on the symptoms, you may also be referred to a paediatrician or allergy specialist for additional support.
 

Step 2: Elimination diet (if indicated)

If CMA is suspected, a healthcare professional may recommend that a milk free diet is followed for 2–4 weeks⁷

• For an exclusively breastfed/chestfed baby, who has not had milk in solid foods and is not having any formula milk, the mother/feeding parent will need to follow a milk free diet for this time
• If the baby is having a mix of breastmilk (human milk) and either formula milk or solid foods containing milk, then it is usually sufficient just to change the baby’s diet and for the mother/feeding parent to continue their normal diet
• For babies on a combination of breast/chest feeds and bottle feeds, if symptoms started when the baby was exclusively breastfeeding/chestfeeding, the mother/feeding parent may also need to be milk free
   

Step 3: Reintroduction (essential)

For suspected non‑IgE allergy, milk should be reintroduced after the elimination period, even if symptoms have improved. Reintroduction only needs to continue long enough to assess for a return of symptoms. If symptoms recur, Cow’s Milk Allergy is likely; if not, it is unlikely. If there is no improvement, other causes should be considered and other treatment options explored with your healthcare professional. The symptoms may be part of a normal developmental stage which will improve with time. Further dietary restriction should be avoided at this time.

Breastfeeding /chestfeeding is strongly recommended to continue wherever possible. It provides important benefits for your baby, including:

• Helping protect against infections
• Supporting gut health
• Breastfeeding/chestfeeding is associated with lower rates of breast cancer in the lactating parent
• Possible reduction in early eczema, wheeze and asthma⁸

A dairy-free (milk-free) diet for the breastfeeding/chestfeeding parent is usually only needed if:

• Cow’s Milk Allergy is strongly suspected
• Your baby has symptoms while exclusively breastfeeding/chestfeeding
• Other causes have been ruled out by a healthcare professional⁷

Only very small amounts of cow’s milk protein pass into breastmilk (human milk), and this can vary between individuals and depending on the type of dairy consumed (e.g. fresh milk vs baked products). Many babies tolerate these trace amounts, even if they react to cow’s milk in formula or solid foods. Therefore, a milk‑free diet for a breastfeeding/chestfeeding parent is not always necessary, and milk can often be reintroduced as the baby gets older, even if breastfeeding/chestfeeding continues.

Although cow’s milk protein typically clears from breast milk (human milk) within 24 hours, it may take 2–4 weeks for the baby’s gut or skin symptoms to settle, so improvement may not be immediate.

Removing milk can affect intake of:

• Calcium
• Vitamin D
• Iodine
• Protein

Foods which are high in calcium could include using fortified plant milk alternatives such as Nut/Oat/Soya Milk or Coconut/Oat/Soya yogurts for example. You can also get calcium from green leafy vegetables and tinned fish with bones.

It is important to ensure adequate iodine intake. Suitable sources include iodine-fortified dairy alternatives (where available), white fish, eggs, and iodine-containing supplements if dietary intake is insufficient.

Protein can be easily achieved if you are having regular protein sources in the diet such as chicken, red meat, eggs, tofu, beans, lentils and nuts.

For any parent producing breastmilk (human milk), even if they have a healthy diet, supplementation of the below is recommend:

• Calcium: 600-1000 mg/day
• Vitamin D: 10 µg/day

Dietetic input is highly recommended to offer individualised support to ensure both the mother/feeding parent and baby achieve adequate nutrition.

Managing Cow’s Milk Allergy (CMA) in a breastfed/chestfed baby can feel like a big change at first, but many parents quickly develop confidence with the right support. The following practical tips can help make day-to-day life easier.

Food ingredient lists will highlight allergens like milk (usually in bold), but milk can also appear under different names.

Common terms to look out for include:

• Casein / caseinate
• Whey / whey powder
• Lactose
• Milk solids
• Butter, cheese, cream, yoghurt
• Ghee or milk fat

If any of these are listed in the ingredients, the product is not suitable for a milk-free diet.

“May contain milk” means there is a risk of cross-contamination. Many babies with CMA can tolerate these small traces. However, always follow your healthcare professional’s advice and when in doubt, speak to a dietitian for clarification.

Adjusting your diet doesn’t mean meals have to be complicated. 

• Base meals around naturally dairy-free foods such as meat, fish, eggs, vegetables, fruits, pulses, and grains
• Think simple: stir-fries, pasta with tomato sauce, roasted vegetables, soups, and curries
• Vegan foods should be milk free but do check the ingredient list, but these can often be quick and safe option

 There are many dairy-free alternatives available, including:

• Plant-based milks (e.g., oat, soya, almond)
• Dairy-free yoghurts and cheeses
• Dairy-free spreads and cooking creams

• Always check ingredients when trying new products
• When eating out, inform staff of your dietary needs—most restaurants are used to managing allergies
• Look up menus in advance where possible to plan suitable options
• Keep a few safe snacks with you when out and about

Over time, these habits become routine and much easier to manage.

It’s completely normal to feel overwhelmed, worried, or frustrated when managing CMA, especially in the early stages. Adjusting your diet while caring for a baby can be challenging!

Try to remember:

• You are doing your best for your baby
• Many babies outgrow CMA
• Support is available such as through the Breastfeeding Network and Allergy UK or your local health visitor or dietitian

A symptom diary can be really helpful, especially when trying to diagnose CMA. It can help spot patterns and identify possible triggers.

Try to record:

• What you eat and drink
• Timing of feeds
• Your baby’s symptoms (what they are, when they happen, and how severe)
• Any changes in behaviour or sleep

When to use it:

• During a dairy-free elimination diet
• When reintroducing dairy

Most cases of Cow’s Milk Allergy (CMA) are mild and can be managed with support. However, it’s important to know when to get medical help.
 

Seek urgent care (call 999) if your baby has:

• Signs of a severe allergic reaction (anaphylaxis)
• Sudden swelling of the face, lips, or tongue
• Difficulty breathing, collapse, or unresponsiveness
• Difficulty swallowing

Contact your healthcare provider if your baby has:

• Severe or ongoing vomiting (especially if unable to keep feeds down)
• Blood in stools
• Poor weight gain or weight loss
• Signs of dehydration (fewer wet nappies, dry mouth, unusual sleepiness)
• Symptoms that do not improve after 2–4 weeks of a dairy-free diet

Also seek advice if:

• You are concerned about your own nutrition while breastfeeding/chestfeeding, especially on a restricted diet

Final message

If you are ever unsure, it is always best to seek advice from your GP, health visitor, or dietitian. Early support can help ensure both you and your baby remain healthy, well-nourished, and confident in managing CMA.

Written by Ellie-May Evans, registered paediatric allergy dietitian in the Southwest of England and Sports Paediatric Specialist at Ellie-May Nutrition.