A blood test showing how white blood cells interact with milk proteins could transform the diagnosis and management of cow’s milk allergy in young children.
The basophil activation test (BAT) is more accurate than standard allergy tests for detecting cow’s milk allergy in children and could reduce the need for oral food challenges in allergy diagnosis.
The study, which was funded by the Medical Research Council (MRC), was led by researchers from King’s College London, and Guy’s and St Thomas’ NHS Foundation Trust.
The BAT 2 milk study looked at the accuracy of BAT in identifying cow’s milk allergy compared to two routinely used allergy tests in 150 children undergoing oral food challenges to cow’s milk. The team found that BAT was more accurate at identifying children who reacted to oral food challenges than either the skin prick or specific IgE tests, particularly in children under two years old. The results also showed that the use of BAT as a standalone test could reduce the need for oral food challenges, which are currently used in the clinic to confirm diagnosis.
Although BAT is not yet routinely used in clinical practice, the researchers believe that wider adoption of the test could transform the diagnosis and management of cow’s milk allergy. The test is also about five times cheaper to perform than an oral food challenge.
Alexandra Santos, Professor of Paediatric Allergy at King’s College London, Consultant in Paediatric Allergy at Evelina London Children’s Hospital and senior author of the study, said: “BAT could offer a major advancement in allergy diagnostics, achieving improved diagnostic accuracy and reducing the need (and waiting times) for oral food challenges. By improving the accuracy of diagnosis, we can ensure children receive appropriate care and avoid the risks and restrictions that come with misdiagnosis, as well as easing the emotional and nutritional burden on families.”
Cow’s milk allergy affects 2% to 3% of babies and young children and is a leading cause of food-induced anaphylaxis. However, existing diagnostic tools often result in overdiagnosis, leading to unnecessary milk avoidance and related nutritional and developmental concerns.
Allergy tests can also be inconclusive as oral food challenges are often needed to confirm the allergy and whether the food can be safely reintroduced into the diet. Oral food challenges involve the consumption of small amounts of the allergen under close medical supervision.
BAT is a laboratory test that measures how basophils (a type of white blood cell) in a blood sample reacts when exposed to allergens, such as milk proteins. Unlike traditional testing methods, which can lack precision, BAT offers a more accurate assessment of clinical allergy and could also offer a safer alternative to oral food challenges. The research, published in the journal Allergy, represents the largest diagnostic investigation of BAT for cow’s milk allergy to date.
- Bartha I, Boyd H, Foong RX, et al. The Basophil Activation Test Is the Most Accurate Test in Predicting Allergic Reactions to Baked and Fresh Cow's Milk During Oral Food Challenges. Allergy. 2025 Aug 13. doi: 10.1111/all.16675. Online ahead of print.