Cow’s milk allergy in babies: everything you need to know

Lactose intolerance in babies

by Emily Gilbert |

An allergic reaction in your baby will make most mums panic – especially if you think it’s to do with feeding. While they aren’t incredibly common, around six to eight per cent of kids under the age of three have a food allergy, and dairy is the most common type.

The good news? A cow's milk allergy is manageable and your baby may even grow out of it by the time they go to school.

If you're concerned about your little one, Specialist Paediatric Dietitian and co-founder of Mini Tummies, Elise Roberts RD has shared the key signs and symptoms of a cow's milk allergy in babies – and what you can do about it.

What is a cow’s milk allergy?

Cow’s milk allergy (now named cow’s milk protein allergy or “CMPA” for short) is an allergy to the proteins found in cow’s milk. This typically happens within the first year of a baby’s life.

When a child has CMPA, their immune system mistakes the protein in cow’s milk for a potential threat, so it tries to fight them off and responds by releasing chemicals that cause allergic reactions.

What are the two types?

There are two types of CMPA: the first is known as “Immediate onset” (IgE-mediated) and the second is “delayed onset” (non-IgE-mediated).

Both types involve an immune system response to cow’s milk protein, but the exact way the immune system is involved is what separates the two. They can be described as ‘immediate’ and ‘delayed’ because of the timings for symptoms showing up.

In immediate onset CMPA, the immune system produces a specific allergy antibody called IgE, and the reactions usually show up within minutes but can take up to two hours, after consuming cow’s milk.

Delayed onset allergy is more common and the symptoms can appear between 2 - 72 hours after consuming cow’s milk. If the cow’s milk protein is a regular part of the diet, these symptoms can become constant.

baby having milk

Cow’s milk allergy symptoms in babies

CMPA is notoriously difficult to diagnose because many of the key symptoms are also common things most babies experience at some point for a number of reasons, for example, diarrhoea, wind, tummy pain and crying. So it’s super important to work with a GP or paediatric dietitian for a diagnosis.

The common symptoms include:

Digestive symptoms: vomiting, diarrhoea, stomach pain, constipation and reflux, and mucus or blood in their poo

Skin symptoms: itching, unexplained rashes, worsening of any existing skin conditions like baby eczema after your baby has cow’s milk.

Respiratory symptoms: difficulty breathing, stuffy nose, wheezing, coughing

General symptoms: particularly for the delayed onset type, you may see colic-like symptoms and irritability

In severe cases, although it’s rare, immediate onset CMPA can cause a life-threatening reaction called anaphylaxis, which would show symptoms of difficulty breathing, swelling of the face or throat, a racing heartbeat, or unusual sleepiness and unconsciousness.

If you spot any of these more serious symptoms, it’s really important to get urgent medical attention, so call an ambulance immediately.

Are cow’s milk allergies common in babies?

CMPA is one of the most common food allergies in infants and it’s estimated to affect around 2% to 7% of babies under the age of 1. Although the exact numbers aren’t totally clear, particularly as it’s tricky to diagnose.

It can happen in both breastfed and formula-fed babies, however, it’s a little more common in babies that are formula-fed, as cow’s milk is a common ingredient in many types of infant formula.

The good news is that most children will grow out of their CMPA by the time they’re around 18 months to 3 years old.

When should I take my baby to a doctor?

Speak to your GP, health visitor or a paediatric dietitian as soon as you start to suspect that your baby may be having an allergic reaction to cow’s milk. Trying to navigate it alone can be very difficult and it’s important to get an accurate diagnosis.

For your appointment, make a note of the symptoms you think they’re experiencing, along with when they started, how long they tend to last and when they appear after they have cow’s milk. It can also be helpful to take photographs of any visible symptoms if you can.

How is a milk allergy diagnosed?

A cow’s milk allergy is typically diagnosed through a combination of taking medical history, physical examination and allergy testing, however, this differs slightly depending on the type of CMPA your baby is suspected of having (whether it’s immediate or delayed).

First, you’ll be asked about your baby’s symptoms in detail, what they had to eat or drink, and other health conditions, as well as whether there was anything else happening around the same time as the symptoms started. Perhaps they started weaning or you introduced formula milk for the first time? This is where making note of the timings is really helpful, so your GP or dietitian can get a clear picture and accurately assess the symptoms.

For immediate-type allergies, you’ll often be referred to an allergy specialist for further testing. The two main tests are:

• A skin prick test, where a small amount of milk protein is dropped onto baby’s skin and the visible reaction is measured

• A specific blood test, which can only be offered by specialist allergy doctors.

While there might be some at-home tests online claiming to identify allergies and intolerances, please don’t waste your money on these. Online allergy tests should be avoided at all costs - at best, they’re not particularly useful, and at worst, they can be misleading. As a worried parent, you deserve the best science-backed support!

For delayed-type reactions, the diagnosis is a little trickier as there’s currently no blood or skin test that can confirm or rule out this type of allergy.

Instead, identifying a delayed allergy is done by excluding and then reintroducing cow’s milk, while closely monitoring the effect this has on your baby’s symptoms. If symptoms get better when cows milk is excluded and then come back when it’s reintroduced, then a delayed onset (non-IgE) allergy diagnosis will be confirmed.

The reintroduction stage can be difficult, especially if you’ve seen a huge change in how well your baby feels when cow’s milk is excluded. BUT, it’s a crucial step in the treatment process and reduces the risk that you might be excluding cow’s milk unnecessarily.

What is the treatment?

Initially, the treatment is complete exclusion of cow’s milk and any foods containing cow’s milk protein, including dairy products like cheese and yoghurt.

If your baby is formula-fed and under 12 months old, you may be prescribed a special hypoallergenic formula, where the cow’s milk protein is already broken down to make digestion easier for your baby.

If you’re breastfeeding, you may also be advised to go milk-free, as the cow’s milk proteins passing from you to your baby through breast milk can sometimes cause a reaction.

For babies with delayed-type allergies, you’ll be advised to exclude cow’s milk for a set time period, usually around 6 to 9 months. After this, your healthcare provider will take you through how to reintroduce cow’s milk in a very gradual and specific way, starting with introducing small amounts of cow’s milk in forms that are more easily managed (such as in biscuits), then slowly working up to introducing whole cow’s milk over a few weeks. This is called working up the “milk ladder”.

For immediate-type allergies, you’ll be supported by a specialist allergy team and it may involve reintroducing cow’s milk in a controlled hospital environment, where a medical team can supervise. This shouldn’t be done alone at home without the advice of your healthcare team, to make sure your baby is well looked after in case of any serious reactions.

How to manage a cow’s milk allergy

Make sure to get clear advice and steps from your GP or dietitian about your baby’s own treatment plan and what symptoms you need to keep an eye out for - ask as many questions as you need to!

In the ‘elimination’ phase, make family and friends, as well as their nursery team where relevant, aware of your baby's diagnosis and remind them not to give your little one any food or drink containing milk. It’s also worth keeping a sharp eye out for any food being shared between little friends. To make things easier, always make sure you’ve got some milk-free alternative snacks on hand for babies over 6 months old.

As cow’s milk is often the main source of calcium for children, it’s also helpful to speak to a dietitian about making sure both you and baby are meeting your calcium needs. You might be recommended to take a calcium supplement and you’ll be given recommendations for calcium-containing foods to include in your meals, such as sardines, soybeans, leafy greens like kale, and fortified plant-based milks.

What is the difference between a milk allergy and lactose intolerance?

The key difference is that in cow’s milk protein allergy, the immune system is reacting to the protein in milk, whereas in lactose intolerance, the symptoms are caused by not being able to digest the sugar (lactose) in milk. Lactose intolerance is much less common in babies and young children.

While the symptoms of lactose intolerance can be similar and equally unpleasant, it is an intolerance, not an allergy. This means it doesn’t involve a response by the immune system. Instead, lactose intolerance happens when the body doesn’t produce enough of a specific enzyme (called lactase) to break down the milk sugar. When lactose isn’t properly digested, it can cause symptoms such as bloating, gas, diarrhoea and tummy pain.

For lactose intolerance, the treatment is to limit or avoid food and drink containing lactose - and there are lactose-free dairy products, as well as lactase supplements available to help.

Lactose-free dairy products aren’t suitable for babies with cow’s milk protein allergy.

About the expert

Elise Roberts RD is a HCPC Registered Dietitian, a children's dietitian for the NHS, and is passionate about supporting young people through nutrition to reach their full potential. She is also the co-founder of Mini Tummies which brings you everything you need to nourish your family and raise happy, confident eaters for life.

Just so you know, whilst we may receive a commission or other compensation from the links on this website, we never allow this to influence product selections - read why you should trust us