How does an elimination diet and food challenge help to diagnose cow’s milk allergy?

green ribbon cmaAfter discussing your baby’s symptoms with your doctor, he or she will want to make a diagnosis. If a non-IgE-mediated allergy is suspected, or if your doctor has carried out some tests for an IgE-mediated allergy but the results were inconclusive, your doctor may advise putting your baby on an elimination diet followed by a food challenge. This is one of the most accurate ways of diagnosing it and answering the question, 'Is it cow's milk allergy?'


1. Elimination Diet

It’s likely that your doctor will ask you to remove cow’s milk protein from your baby’s diet for a few weeks to see if their symptoms improve. This could suggest that the protein was responsible for your baby’s symptoms.

How you eliminate cow’s milk protein from your baby’s diet depends on whether you’re breastfeeding or giving formula feeds. In either case, it’s important that you don’t make any changes to your baby’s diet without the supervision of a healthcare professional.

Breast-fed babies

Breast milk provides the best nutrition for your baby, so it’s important to continue breastfeeding. However, your doctor might advise you to remove products that contain cow’s milk protein and dairy from your own diet, as this could be passed to your baby through your breast milk. You may be referred to a specialist to help you design a diet that is not only cow’s milk protein-free, it will ensure you get all the right nutrients to help keep you and your baby healthy.

Which foods contain cow’s milk protein?

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Formula-fed babies

Your doctor will advise you to put your baby onto a special hypoallergenic formula designed for babies with cow’s milk allergy, where the cow’s milk proteins have been broken down so they’re no longer recognised by your baby’s immune system. This means that they’re unlikely to cause an allergic reaction in babies with cow’s milk allergy.

There are different types of hypoallergenic formula, two of which are: extensively hydrolysed formulas (suitable for the vast majority of babies with cow’s milk allergy); and amino acid-based formulas (suitable for those with severe cow’s milk allergy or multiple allergies). In fact, extensively hydrolysed formulas are effective in at least 90% of infants with cow’s milk allergy. This is the accepted choice for managing this condition in the vast majority of cases. A small number of babies might continue to have symptoms on this, and will need to be switched to an amino acid-based formula to notice improvements. This type of elimination diet might need to be tried for 2–6 weeks before an improvement is seen.

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2. Food challenge

After eliminating cow’s milk protein from your baby’s diet for a couple of weeks, your doctor may advise a food challenge to be done. This involves feeding your baby a tiny amount of milk-based product and carefully monitoring for any signs of an allergic reaction. It’s important that a food challenge is only done under the supervision and recommendation of a healthcare professional and may be carried out in hospital. This would involve gradually giving your baby more and more cow’s milk protein over a period of a few hours, and monitoring for any signs of an allergic reaction.

Depending on how severe your baby’s original symptoms were, your doctor might advise you to do this food challenge at home – where you need to gradually reintroduce cow’s milk protein into your baby’s diet and note down any changes in their behaviour.

If an allergic reaction is seen…

This confirms a cow’s milk allergy diagnosis. Your baby will then need to be kept on the elimination diet until your doctor requests another food challenge to see if your baby has grown out of the cow’s milk allergy.

If an allergic reaction isn’t seen…

Even if an allergic reaction isn’t seen at the time of the challenge, delayed symptoms could show later.

If you’ve been into hospital for the food challenge, and no signs of an allergic reaction were seen at the time, it’s possible that your doctor may advise you to go home and gradually reintroduce certain forms of cow’s milk protein back into your baby’s diet whilst monitoring for any symptoms – your doctor will explain exactly how you should do this. It’s important that you only reintroduce cow’s milk protein into your baby’s diet under the supervision and recommendation of a healthcare professional.

If your baby doesn’t show any signs of an allergic reaction following a food challenge, your doctor will investigate if there are any other causes of your baby’s symptoms.

You can find more information about the tests used in the UK to diagnose cow’s milk allergy from the National Institute for Health and Care Excellence (NICE).

Cow’s milk allergy isn’t always easy to diagnose, as the symptoms can be similar to the ones in some other conditions, such as colic. Your doctor may need to rule out these other conditions in order to pinpoint the right diagnosis.