Infant Milk Allergy, Lactose Intolerance, or Something Else?

Reviewed by Hansa D. Bhargava, MD on January 20, 2021
newborn with rash on face

If your baby seems to react badly to infant formula milk, you're probably wondering why it's happening. Maybe you think it's a cows' milk allergy or lactose intolerance.  

Lots of people think those problems are the same, but they’re not. Some of the symptoms they cause may be similar, so it can be confusing. Or it might not be either of those things. Your GP will help you work out what's going on.

What Is Cows' Milk Allergy?

Most infant formula milk is made from cows' milk. The first time a baby has cows' milk, it's very likely to be in formula. That's because cows' milk itself isn't recommended as a drink for children under the age of 1. But from around 6 months old, when a baby is being introduced to solids, they can have cows’ milk as an ingredient in foods.

Cows' milk allergy is one of the most common allergies for babies and young children. Experts estimate that 2% to 7.5% of U.K. babies under 12 months old have it. If it happens, your child's immune system reacts to the proteins in milk, triggering allergy symptoms. That's why it's sometimes called cows' milk protein allergy.

If your baby does get an allergy to cow's milk, it usually starts when your baby is first exposed to cow's milk, through formula, or later with solid foods.

Sometimes, but not very often, babies who are breastfed can have this allergy. It's because the cows' milk from the mum's diet is being passed on to the baby through their breast milk.

Most children grow out of the allergy by the time they reach the age of 5. 

Symptoms of Cows' Milk Allergy

Your child may have symptoms within minutes of having cows' milk or formula made from it. In other cases, problems might not happen until hours or even days afterward.

There are lots of possible symptoms:

  • Digestion problems, including tummy ache, being sick, diarrhoea, and constipation
  • Skin reactions, such as swelling of the lips, face, and eye area, and a red, itchy rash
  • Hay-fever-like symptoms, such as a runny nose and watery eyes
  • Eczema that doesn't get better with treatment

Sudden, severe symptoms are rare but can include swelling of the mouth or throat, wheezing, shortness of breath, and difficulty breathing -- a severe allergic reaction called anaphylaxis, which can also make your child feel faint or become unconscious. This is a medical emergency that requires calling 999 or going to A&E immediately.

Treatment for Cows' Milk Allergy

If your baby is found to be allergic to cows' milk, your GP or allergy specialist will explain to you how to manage it. This will include removing all cows’ milk from your child’s diet for a period of time. Your GP may also prescribe a special infant formula that doesn't contain cows' milk for bottle-fed babies.

If your baby gets a cow’s milk allergy in reaction to the dairy you eat or drink, your GP may tell you to avoid cows’ milk products in your diet in case these affect your baby.

this is the case, your GP may tell you to avoid cows’ milk products in your diet in case these affect your baby.

Your GP or dietitian will help you work out the best diet for your child at whatever stage they are at and closely follow your child's progress. Your doctor will suggest reintroducing milk after a while to see if your child has grown out of their allergy.

What Is Lactose Intolerance?

Your child may have a different type of reaction to cows' milk, or formula made from it, called lactose intolerance. This is when their body can't digest lactose, which is a type of natural sugar found in milk.

About 70% of people in the world have lactose intolerance. It's more common among people from Asian, African, and Hispanic ethnic groups.

Babies and young children can also become temporarily intolerant to lactose after they've had a tummy bug or another condition.

Symptoms of Lactose Intolerance

Some of the symptoms of being intolerant to lactose are similar to those of a cows' milk allergy. These may include digestion problems such as tummy aches, bloating, and wind. Diarrhoea can also be a symptom. 

Treatment for Lactose Intolerance

Your GP will help find out if your child is lactose intolerant. Your child may be given a lactose intolerance test, which measures blood sugar levels before and after having a lactose solution drink.

If the test confirms lactose intolerance, your child will likely be referred to a dietitian, who will give you advice on what foods and drinks are suitable. Babies and young children need to get the right nutrients to make sure they grow and develop properly.

For bottle-fed babies with lactose intolerance, your GP will probably advise you to switch to a lactose-free formula milk.

If you are breastfeeding, it may help if your baby has lactase substitute drops, which make it easier for them to digest lactose in breast milk.

Lactose intolerance is often only temporary for many babies and young children. Their symptoms will often get better within a few weeks. At this point, it's safe to start gradually bringing milk and dairy back into their diet.

Something Else?

If your baby or small child doesn't handle formula milk very well, it may be something else altogether.

Some of the symptoms of lactose intolerance and milk allergy are common in babies for other reasons, so it can be tricky to work out what's causing the problem.

It may be reflux. This is when your baby brings milk back up during or after a feed. Most babies bring milk back up sometimes, but for some babies, it can happen a lot and be painful. It can give them tummy ache, make them feel uncomfortable, and make it harder for them to feed and gain weight.

It may be colic. This is when the baby cries a lot and you can't work out why. Colic can make babies grizzly and give them windy tummies, which can also be symptoms of an allergy or intolerance to milk.

If your baby or child is having any problems with feeding, isn't putting on weight, or is showing any other symptoms you are concerned about, go to the GP. They can help figure out what the problem is and how to fix it.

Show Sources


NHS: "What Should I Do If I Think My Baby Is Allergic or Intolerant to Cows' Milk?"

National Institute for Health and Care Excellence (NICE) -- Clinical Knowledge Summaries: "Cows' Milk Protein Allergy in Children."

NHS Great Ormond Street Hospital for Children: "Lactose Intolerance."

NHS Eat well: "Dairy and alternatives in your diet."

NHS Start4Life: "What is Reflux?"

NHS Conditions: "Colic."

Allergy UK: "Allergy Prevalence Useful Facts and Figures."

National Childbirth Trust -- Formula Feeding: "What's in Infant Formula?"

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