Cow’s Milk Protein Allergy: What Every Parent Should Know

Cow’s Milk Protein Allergy (CMPA) is one of the most common food allergies in babies and young children, thought to affect around 5-7% of children.  Whilst awareness of Cow’s Milk allergy is growing, it can still often be challenging to diagnose, and symptoms may be mistaken for other common infant issues like colic, reflux, or general feeding discomfort. This can leave parents feeling confused, overwhelmed, and unsure of how to help their child. Understanding the signs, diagnosis process, and management strategies for Cow’s Milk Protein Allergy is crucial in ensuring your child gets the right support.

In this blog, we cover;

• What is Cow’s Milk Protein Allergy(CMPA)?
• What are the symptoms of Cow’s Milk Protein Allergy CMPA?
• Is it milk allergy or milk intolerance?
• How is CMPA diagnosed?
• What if you’re weaning a baby with CMPA?
• My child is allergic to milk, do they need to avoid soy too?
• Will your child outgrow their milk allergy?

What is Cow’s Milk Protein Allergy

Cow’s Milk Protein Allergy (CMPA) is an overreaction of the immune system to one or more of the proteins found in cow’s milk.  Whilst for most children, their body recognises these proteins as safe,  in the case of children with CMPA, their body’s immune system is getting it wrong and considers these proteins as a threat.  As a result, babies or children with CMPA can develop a series of symptoms following consumption of cow’s milk protein either via formula milk, food and/or in some cases via mum’s breastmilk.  

Children with CMPA usually show symptoms that are either immediate (IgE-mediated) or delayed (non-IgE-mediated). IgE stands for Immunoglobulin E, which is a protein of the immune system known as an antibody. These antibodies are quickly released by the body in response to an allergen  –  in this case, milk  –  and are present in any immediate type allergic reactions. However, they are not released during delayed-type allergic reactions; instead, a different immune pathway that does not involve these antibodies causes delayed allergic reactions to food, hence the term non-IgE-mediated.   

What are the symptoms of Cow’s Milk Protein Allergy?

Symptoms of a cow’s milk protein allergy will depend of the type of reaction a baby is having

Immediate symptoms of food allergy will occur within minutes up to 2 hours after consumption of a food – in this case, cow’s milk, and can affect:

• The skin e.g. hives, flushing, itching, swelling, immediate eczema flare
• The digestive system e.g. vomiting, diarrhoea
• The breathing system* e.g. swelling of lips/tongue/mouth/throat, hoarse cough or cry, wheezing, floppiness/collapse 
• In rare, but severe circumstances, an immediate reaction can lead to anaphylaxis*

(*Always seek immediate medical intervention via 999)

Delayed symptoms of a food allergy, can occur 2-72hours after consumption of a food, and symptoms can affect:

• The skin, e.g. itching, early onset and persisting eczema, difficult to manage despite treatment
• The digestive system e.g. vomiting, diarrhoea, constipation, reflux, colic, mucus and/or blood in stools 
• Other, e.g. difficulty with growth, feed or food refusal, persistently disturbed sleep

Milk allergy or intolerance?

Cow’s milk protein allergy is often (incorrectly!) called ‘milk intolerance’ and is most frequently mistaken for lactose intolerance; however, allergy and intolerance are very different conditions. Whether a child’s symptoms are immediate or delayed, both responses result from the immune system’s interaction with cow’s milk protein and are food allergies. 

Intolerance, such as lactose intolerance, does not involve the immune system. It usually occurs when there is difficulty digesting one or more components of a food. For lactose intolerance, symptoms arise due to the lack of an enzyme called lactase in the gut, which helps break down lactose. Lactose, the sugar found in milk, is unrelated to an immune response to cow’s milk protein in cases of CMPA.  Lactose intolerance in babies is also very rare!

Some children diagnosed with CMPA may also have a temporary lactose intolerance (often if they have experienced persistent diarrhoea), but this condition can improve with time, whilst the enzyme which helps digest lactose returns to normal levels in a child’s gut.

How is Cow’s Milk Protein Allergy diagnosed?

The gold standard for diagnosing cow’s milk allergy is a detailed allergy-focused history taken by a clinician with a background in food allergy, such as an allergy doctor or dietitian. They will ask questions about symptoms, which foods or milk were consumed, how quickly symptoms appeared, and what these symptoms were. With this in mind, if you suspect your child has a milk allergy, it can be helpful to keep a food and symptom diary, along with any pictures or videos of symptoms of concern, e.g., nappy photos, skin rashes.

If your child has a suspected immediate type (IgE-mediated) cow’s milk allergy, your clinician may also perform allergy testing such as a skin prick test and/or blood test. These tests aim to detect IgE antibodies, in this case to milk proteins. A positive result (exceeding a certain threshold) suggests a higher likelihood of an allergy to milk, but it is important to note that a higher test value does not indicate a more severe allergy, only that the child is more likely to react to that food.

If your child has a suspected delayed-type food allergy, there are no validated tests to use alongside the history. There is no point in conducting tests for immediate food allergies, as the same immune proteins (IgE antibodies) are not present in delayed reactions. The only true ‘test’ is to remove milk from the child’s diet for 2-4 weeks, or adjust their milk intake, or remove milk from a breastfeeding mother’s diet if necessary, then reintroduce it later. If a child has a delayed milk allergy, symptoms should resolve during the exclusion period, and should recur once milk is reintroduced. This process should ideally always be done under the guidance of an allergist or dietitian.

What about weaning with CMPA?

While it can be easy to worry about what to offer your baby with a milk allergy when weaning, the overall principles of starting solids remain the same. The key things you’ll have to be aware of are:

1. Avoiding foods which contain cow’s milk, but checking labels carefully
2. Replacing dairy products with suitable fortified milk-free alternatives
3. Safely introducing other common allergenic foods into your baby’s diet

Your baby will still be able to include a wide range of foods across all other food groups to establish a balanced and varied diet, including:

• Fruit and vegetables
• Starchy foods like potatoes, rice, pasta, grains, cereals and baked products 
• Protein-rich foods such as meat, fish, eggs, beans, lentils, pulses, soya*
• Suitable dairy alternatives
• Higher fat food, e.g. oils, suitable spreads, nuts and seeds (in an age-appropriate form)

My child is allergic to milk; do they also need to avoid soy?

For babies and children with CMPA, caution is often advised regarding soya intake mainly because of the risk of cross-reaction between milk proteins and soya proteins. Based on current scientific knowledge, it is estimated that about 50% of children with non-IgE (delayed) CMPA may cross-react with soya. However, this risk appears to decrease to around 10-15% in those with an immediate-type milk allergy.

Therefore, deciding whether to introduce soya as a milk alternative can be a difficult choice for many parents, especially since soya is present in many pre-prepared foods and can be a nutritious milk alternative. Some prefer to avoid it altogether or are advised to do so, while others may be willing to trial soya directly to assess tolerance, with guidance from a health professional. If you decide to trial introducing soya into your child’s diet, seek support and advice from a health professional and refer to our guidance pack on introducing allergens.

Other concerns surrounding soya consumption that are often raised are regarding the safety of use in young children, with many myths still flying around. Whilst the use of soya formula under 6 months of age is not currently recommended in the UK, the introduction and use of soya in foods from 6 months of age and as a drink after 1 year of age are considered safe. Soy consumption has also been linked to numerous health benefits, and if tolerated, can be a valuable source of protein, iron, and calcium while following a milk-free diet.

Will my child outgrow their Cow’s Milk Protein Allergy?

The good news for many families is that around 80% of children outgrow their cow’s milk allergy by the time they reach school, and for many, this is often much sooner, by 3 years of age.  For a child with a delayed type food allergy, you’ll likely be recommended to commence the milk ladder around 9-12 months of age onwards, this is a stepwise reintroduction to milk, starting with milk proteins in a very low dose in their least allergic form (baked in a wheat matrix).  You can read more about the milk ladder here.  

For children with immediate-type milk allergy, the allergy team will determine the safest way to reintroduce milk. This could be through a hospital food challenge or by using a modified milk ladder to carefully introduce some baked milk at home under supervision.

There is growing evidence of the benefits of reintroducing some milk, especially baked milk, early into children’s diets to support their development of tolerance; however, this advice must be tailored to your child by an allergist and/or specialist children’s dietitian.