Which allergy tests can help to diagnose cow’s milk allergy?

green ribbon cmaIf your baby's symptoms are starting to make you think, 'Is it cow's milk allergy?', speak to your doctor, they will ask you some questions about your baby’s symptoms and may carry out certain tests. Your baby might be referred to a hospital specialist.

If the doctor suspects that your baby might have an IgE-mediated food allergy, where the symptoms of an allergic reaction happen immediately (within a few hours) after eating or drinking anything containing cow’s milk protein, he or she might consider doing an allergy test such as a skin prick or blood test to help find the right diagnosis. Please remember, though, that these tests will not reveal if your baby has a non-IgE-mediated food allergy.

Which foods contain cow’s milk protein?

Skin prick test

Skin prick testing (SPT) in an allergy clinic demonstrates an allergic response to a specific allergen and can help to confirm if your baby has an allergy to cow’s milk protein. SPT is simple, safe and quick, providing results within 15–20 minutes.

A tiny amount of cow’s milk protein solution is put into the skin, which might cause a small, localised allergic response in the form of a bump and redness. If your doctor isn’t sure whether your baby is allergic to cow’s milk protein or to something else, he or she might test a few different things at the same time.

Good to know

The results need to be interpreted alongside your baby’s medical history and other factors. This is why it’s important that a skin prick test is only carried out by a qualified doctor in an allergy clinic. Please don’t use any tests sold on the high street or online as they may not be reliable; also, the advice and information that they give may not be safe or appropriate for your baby

You can find out more about the skin prick test from the charity, Allergy UK.

Blood test

In some cases, the doctor might recommend doing a blood test if the skin prick test isn’t practical (for example, if your baby has extensive eczema) or to confirm the results of the skin test.

With a blood test, your baby’s blood is taken at the doctor’s surgery and sent to a laboratory. There, it will be analysed to see if it contains a type of antibody called IgE antibodies. In people with IgE-mediated cow’s milk allergy, the immune system produces IgE antibodies in response to cow’s milk protein, which triggers an allergic reaction. Therefore, if this blood test shows there is a high level of a specific IgE antibody, this suggests that your baby has had an allergic reaction.

The blood test results can take several days or weeks to come back. You can find out more about the blood test from the charity, Allergy UK.

Both the skin prick test and blood test are relatively simple but they won’t be able to detect non-IgE-mediated cow’s milk allergy. Even if the results come back negative, there’s still a chance your baby could have cow’s milk allergy.

My daughters paediatrician

If your doctor suspects that your baby might have non-IgE-mediated cow’s milk allergy, or the skin prick and/or blood test results come back negative but other signs still suggest that your baby has an allergy, your doctor may suggest putting your baby on an elimination diet followed by a food challenge. (And remember, it is vital that this is only undertaken with the supervision of a healthcare professional.) Although this is more difficult to do, it is one of the most accurate ways of diagnosing cow’s milk allergy.