A new review published in the journal JAMA Pediatrics in April 2020 raises the concern that there may be a significant overdiagnosis of cow's milk allergy in babies and young children, stemming from the use of current medical recommendations.
The study was carried out by researchers at the Imperial College London and Sechenov University in Moscow. They examined official guidelines put out by nine different organizations to diagnose cow's milk allergy, between 2012 and 2109. These recommendations came from several countries, mostly in Europe.
What is milk allergy?
Milk allergy is most typically diagnosed in children less than two years old. Researchers have traditionally classified it as IgE-mediated and non-IgE mediated. In the former type, the allergic reaction involves the antibody component called immunoglobulin E, which causes symptoms like vomiting, raised red rashes on the skin, and very rarely, a life-threatening reaction termed anaphylaxis that causes breathing problems. It can be reproducibly diagnosed by a skin test.
The non-IgE type is different. While the symptoms may include vomiting, loose stools, and excessive crying, these are highly non-specific and are, moreover, far too frequently complained of in healthy young babies to be considered a pointer to any pathological condition.
How many children have cow's milk allergy?
The team of researchers discovered that symptoms like excessive crying, milk regurgitation, and loose stools were often listed as symptoms of cow's milk allergy by many of the guidelines. On the other hand, these symptoms are often commonly found in healthy babies as well.
Using earlier data, from a recent birth cohort study in Europe, including more than 12,000 babies in 9 different countries, only about 1% were diagnosed with cow's milk allergy. However, in some other studies, the percentage of families who thought their children had such an allergy was as high as 14%. Also, between 2000 and 2018, in countries such as Australia and England, there was a sharp increase in the number of prescriptions for specialist formulas for babies who had cow's milk allergy. On the other hand, studies have generally shown no change in the incidence of this condition over time.
The official guidelines on how to identify cow's milk allergy could be one of the possible causes for this rise in false diagnoses, according to the study.
How is cow's milk allergy diagnosed?
According to Dr. Daniel Munblit of Sechenov University, "In the nine guidelines we studied, seven of them suggested including milder symptoms as an indication of non-IgE cow's milk allergy, such as regurgitating milk, crying and rashes - but many of these symptoms are present normally in babies, and will get better with time. Non-IgE cow's milk allergy affects less than 1 percent of infants, whereas troublesome vomiting, crying, or eczema each affect 15-20 percent of babies."
Were the studies unbiased?
The researchers also looked into the possibility of a conflict of interest on the part of the guideline authors. A conflict of interest is when a study is funded by a company that profits from the advice or results obtained from the study. They found that eight of ten of all the authors had such a conflict of interest with companies manufacturing baby formula. Three guidelines were funded directly from such companies or their marketing consultants.
Researcher Dr. Robert Boyle said, "Formula manufacturers may gain from promoting increased cow's milk allergy diagnosis - by influencing practitioners and parents to use a specialized formula in place of a cheaper formula, and by potentially undermining women's confidence in breastfeeding, so that specialized formula is used in place of breastmilk."
To mothers of allergic infants: don't drink cow's milk?
Another controversial area involves the finding that 7 of 9 guidelines say women who are breastfeeding should eliminate all dairy from their diet in case the baby is suspected of having cow's milk allergy. The authors of the current study, on the other hand, say that after analyzing 13 studies on the composition of breast milk, they conclude that this is entirely unnecessary.
The team looked at earlier research results showing how much of the protein called beta-lactoglobulin, which is a cow's milk protein sometimes associated with an allergic reaction, was present in breast milk at extremely low concentrations. The amount of this protein in breast milk, obtained from the mother's gut, can be measured in micrograms (a millionth part of a gram). This would be far too little to cause an allergic reaction in 99% of children with cow's milk allergies who were on breast milk.
The study says, "Clinical trials do not provide consistent support for using maternal or infant cow's milk exclusion" to deal with these common symptoms unless the infant is proven to have cow's milk allergy.
What is the take-home?
The new study throws doubt on the validity of many official guidelines used to identify infants with cow's milk allergy, points out their tendency to overdiagnose, and advises care before making this diagnosis.
As Dr. Boyle explains, "Many infants who are labeled as having milk allergy don't have the condition. Having a child with suspected milk allergy can be a stressful time for any family. Misdiagnosing milk allergy could lead to another condition with similar symptoms being missed, or breastfeeding mothers needlessly following restricted diets - or even stopping breastfeeding altogether. It can also lead to families and the NHS unnecessarily paying for expensive specialist formula."
The conclusion he draws is that pediatric care organizations need to "critically appraise" the guidelines in current use and make sure that such guidelines are not developed by those who may profit from them. On the other hand, doctors should also make sure that cow's milk allergy is accurately diagnosed to avoid the multiple issues associated with a wrong diagnosis.