Cow’s milk allergy in  babies

A cow’s milk allergy in babies is also known as a cow’s milk protein allergy (CMPA). It typically develops when cow’s milk is first introduced into your baby or child’s diet, either when formula feeding or when your baby starts eating other dairy and milk products when they start weaning. 

More rarely, babies who are exclusively breastfed can also develop a cow’s milk protein allergy. This is because, if you’re breastfeeding, it’s possible for the cow’s milk you consume in your diet to pass to your baby through your breast milk².

It’s common for babies who are allergic to cow’s milk to be allergic to goat’s and sheep’s milk, too. This is because they contain similar proteins that can result in an infant dairy allergy.

If you think your baby could have a cow’s milk protein allergy, it’s important to talk to your doctor to establish whether this is the case. If it’s confirmed, you might be referred to a dietitian to discuss how to manage it as your baby grows².

There are two main types of cow’s milk allergy in babies²:  

• Immediate cow’s milk allergy. With this type of milk allergy, symptoms occur immediately, usually within minutes, of your baby consuming cow’s milk.
• Delayed cow’s milk allergy. Here, the symptoms tend to be delayed by several hours, or sometimes days, from when your baby consumes cow’s milk.

If your newborn has an allergic reaction to cow’s milk,  they’re very likely to have several symptoms. Take a look below to help you spot the signs².

If you notice any of these symptoms, it’s always best to talk to your GP or other healthcare professional so that they can rule out or diagnose a cow’s milk allergy.

Very rarely, a cow’s milk allergy can cause a severe allergic reaction known as anaphylaxis. If your baby displays any of the following symptoms, call for an ambulance immediately³:

• Swollen lips, throat, tongue and/or mouth.
• Struggling or unable to breathe - fast breathing, choking, gasping or wheezing.
• Skin or lips turning blue.
• Becoming limp or floppy or not responding as they usually would.

Usually, diagnosing a cow’s milk allergy involves a detailed allergy focused history taken, potentially followed by a combination of tests or a series of elimination and reintroduction diets to get to the bottom of things depending on the type of cow’s milk allergy that is suspected.

When you speak to your healthcare professional, they’ll first ask you some questions to learn more about your little one’s symptoms. How quickly or slowly they appeared, for example, whether your baby has started weaning and if they have any existing conditions⁴.

Your healthcare professional will then advise whether or not further testing is needed.

If a delayed infant dairy allergy is suspected, there aren’t any specific tests that can help with a diagnosis. Instead, your healthcare professional may advise eliminating all cow’s milk protein from your baby’s diet, and, if they’re formula-fed, they may prescribe a hypoallergenic formula. If your baby is exclusively breast fed, you’ll need to eliminate all cow’s milk protein from your own diet to see how your baby responds².

This type of elimination diet must always be carried out under the supervision of your healthcare professional and will usually last anywhere between 2-4 weeks².

Two types of tests are available if an immediate infant dairy allergy is suspected: a skin prick test or an antibody blood test will be carried out by an allergy specialist.

Here, a small drop of the allergen will be placed on your little one’s forearm, and a small scratch will be made through the droplet. If an itchy, white, raised lump or spot appears, your baby has tested positive for a cow’s milk allergy. 

Whilst the skin prick test⁵ might cause your baby some discomfort and itchiness, it’s completely safe - lots of cuddles and some play time should do the trick. 

Also known as a Specific IgE blood test⁵, this involves taking a sample of your baby’s blood to test for an allergy antibody to a specific food - in this case, cow’s milk. It’s most commonly carried out in cases where a skin prick test can’t be carried out, for example, if your baby suffers from eczema. 

Sometimes, because the symptoms can be so similar, it can be tricky to know whether your baby has a cow’s milk allergy or a lactose intolerance. Knowing how to recognise each can help you get a quicker diagnosis and manage the condition more effectively.

So, how can you tell the difference?

If your baby has a cow’s milk allergy, their immune system will react to one or more of the proteins found in milk. Symptoms usually affect your baby’s skin, gut, breathing and circulation⁶.  

A lactose insensitivity or intolerance in infants is very rare, and occurs when  your baby doesn’t produce any or enough lactase, an enzyme that breaks down lactose. Symptoms include diarrhoea, bloating and wind6. There are two types of lactose intolerance: primary and secondary.

Primary lactose intolerance is genetic and occurs when you lose the ability to produce lactase over time. It’s very rare and doesn’t usually affect babies⁷.  Secondary lactose intolerance isn’t related to the immune system and is caused by damage to the gut, such as a cow’s milk allergy or gastroenteritis⁸. It’s usually temporary and will get better once the gut gets better.

Between 2-5% of babies under the age of one are thought to be affected by a cow’s milk allergy⁹, and it’s one of the most common food allergies seen in children¹⁰. The good news is, however, that by the age of five, most children will have grown out of it¹¹.

Providing your doctor with as much information as possible about your baby’s symptoms will help them to make a diagnosis - the more evidence and information you can provide, the better.

It’s a good idea to keep a diary of your baby’s symptoms, as this can help your doctor identify or rule out a cow’s milk allergy. For example, if your baby comes out with a rash after feeding, take a photo and record how long it took for the rash to appear and how long it lasts. In addition, note any vomiting, diarrhoea, stomach cramps or difficulty breathing if these symptoms happen when your little one is eating or drinking.

If your baby is diagnosed with a cow’s milk allergy, you’ll probably have a lot of questions about how to manage it, especially when it comes to their diet. 

Once you know the cause of your baby’s symptoms, your GP or other healthcare professional will discuss the treatment options with you and can give you all the advice you need to keep them healthy.

You might be referred to a dietician who will look at the foods your baby is eating and make any necessary adjustments to their diet².

Managing a cow’s milk allergy in babies and children involves removing all cow’s milk from their diet¹².  

When introducing solid foods to a baby with a cow’s milk allergy, you'll need to get familiar with reading food labels and their ingredients, as milk can be found in unlikely places even when you least expect it.

Whilst this might seem overwhelming at first, keep in mind that food labelling laws are there to help you, and common allergens, like milk, must be declared on pre-packaged foods.

Breast milk is the best nourishment for your baby, even if they’ve been diagnosed with a cow’s milk allergy.

While cow’s milk protein can pass into breast milk from your diet, most babies with a cow’s milk allergy can tolerate it¹³. In rare cases, babies do react to these milk proteins passing though their mothers’ breast milk. If this happens, your healthcare professional or doctor may advise you to avoid all dairy products to see if this makes a difference to your baby’s symptoms^{14, 15}. 

You should only eliminate dairy from your diet on the advice of a doctor or other healthcare professional, for example, a dietician or allergy specialist. This is to ensure you’re not missing out on other vital nutrients you need.

When breastfeeding, you need 1,250mg of calcium every day16. That’s 550mg more than you’d usually need. This is typically achieved by regularly drinking low-fat milk and eating foods like cheese, yoghurt and other healthy milk products up to five times a day.

Most people get the majority of their calcium from dairy products. So, if you’ve been advised to follow a dairy-free breastfeeding diet, it’s important to boost your calcium intake in other ways. For example, by eating plenty of other dairy and milk-free sources of calcium instead. These include¹⁶:

• Tinned sardines with the bones.
• Calcium-fortified fruit juices.
• Milk-free calcium enriched oat, rice or nut drinks. Babies with a cow’s milk allergy can also react to soya milk, so this is best avoided.  
• Green, leafy vegetables such as kale.
• Calcium-fortified bread.

Vitamin D can help your body absorb calcium from food¹⁶. As such, it’s recommended that all adults and children over one year take a 10mg vitamin D supplement every day¹⁷.

Speak to your healthcare professional about your calcium and vitamin D intake to ensure you’re getting what you need.

If your baby is formula feeding and has been diagnosed with a cow’s milk allergy, your doctor or dietitian will prescribe a special hypoallergenic formula. The type of special formula that your baby needs will depend on their age, growth, severity of symptoms and nutritional requirements. 

Your baby may be prescribed a special kind of extensively hydrolysed formula. Here, the proteins in the milk have been broken down into smaller pieces, so your baby’s immune system is less likely to recognise them as an allergen.

Rest assured that this process doesn’t affect the nutritional value of the formula, and it will still provide the wide range of nutrients, including vitamins and minerals, that your baby needs.

It’s normal for your baby’s feeding patterns and habits to change when you switch to an extensively hydrolysed formula, and it may take your baby a couple of weeks to get used to their new milk. You may also notice that their stools may be different, becoming looser and greener in colour. In more severe cases of cow’s milk allergy or where an extensively hydrolysed formula doesn’t resolve all your baby’s symptoms, they may be prescribed an amino acid formula.

Many milks aren’t suitable for babies with a cow’s milk allergy; for example, soya-based infant formulas aren’t recommended for babies under six months old.

This is because they contain plant-based compounds with oestrogen-like properties known as phytoestrogens. Some infants with a cow’s milk allergy may also be sensitive to soy protein, and research has shown that 30–50% of babies who react to cows’ milk-based formulas might also react to soy-based formulas¹⁸.

Another formula unsuitable for babies with a cow’s milk allergy is partially hydrolysed formula. The proteins in this type of milk are only partially broken down and can still cause an allergic reaction¹⁹.

If you’re concerned that your baby has a cow’s milk allergy and you want more information on diagnosis or the side effects of cows’ milk alternatives, it’s very important to consult your doctor or healthcare professional and not self-prescribe with over-the-counter milk alternatives.

As we’ve said above, a cow’s milk allergy can be challenging to diagnose, given the variety of symptoms and potential causes. While the actual incidence of cows’ milk allergy is only around 2-5%⁹,  it’s estimated that up to 15% of babies may show symptoms that suggest a cow’s milk allergy might be at play.

As such, it’s important that you don’t self-prescribe or make any significant changes to your or your baby’s diet without the advice of a doctor or dietitian.