As part of the diagnosis process, healthcare professionals may suggest putting a baby on an elimination diet followed by a food challenge. If it is suspected that the cow’s milk allergy was IgE-mediated, healthcare professionals may also recommend a skin prick or blood test.

Elimination diet

An elimination diet involves removing cow’s milk protein from a baby’s diet for a short period of time, and then monitoring the effect this has on their symptoms. Healthcare professionals may recommend that foods containing cow’s milk protein are completely removed from the diet of breastfeeding mums. For formula-fed babies, healthcare professionals may recommend that the baby is switched onto a special hypoallergenic formula designed for babies with cow’s milk allergy. The healthcare professional would advise on how to begin the elimination diet and how long to continue for. A trial of up to 4 weeks is usually given.

If a healthcare professionals recommended a hypoallergenic formula as part of an elimination diet, it won’t contain whole cow’s milk protein so in most cases should no longer be recognised by the immune system as harmful. It could be an extensively hydrolysed or an amino acid-based formula. Extensively hydrolysed hypoallergenic formulas are effective in approximately 90% of babies with cow's milk allergy.

If a baby is diagnosed with severe cow’s milk allergy or multiple food allergies, or their symptoms do not resolve after trying an extensively hydrolysed formula for a trial period, healthcare professionals may recommend an amino acid-based formula. Find out more about what these suitable milks and formulas could be.

Food challenge

After a baby has been on a cow’s milk protein elimination diet for a few weeks as recommended by a healthcare professional and symptoms have improved, an ‘oral food challenge’ may be advised. This involves feeding the baby a small amount of a milk-based product and carefully watching for any signs of reactions. This process may take place at a doctor’s surgery or hospital clinic, or the healthcare professional may ask for a routine cow’s milk-based infant formula to be gradually reintroduced into the baby’s diet at home and any changes noted. It’s important that this is only done with the advice and supervision of a healthcare professional.

If an allergic reaction isn’t seen at the time of the challenge or later on, the healthcare professional may investigate other possible causes of the baby’s symptoms, such as colic or lactose intolerance. If an allergic reaction is seen, the diagnosis of cow’s milk allergy can be made. The baby may then need to remain on the elimination diet until they grow out of their allergy. When and how to test whether they can start to return to a normal diet would be advised by the healthcare professional.

Elimination and challenge