Guidelines may promote over-diagnosis of cow’s milk allergy in infants

Press release issued: 8 December 2021

International guidelines developed to help doctors diagnose cow’s milk allergy may lead to over-diagnosis, according to University of Bristol-led research published in the journal Clinical and Experimental Allergy today [8 December]. The study found that three-quarters of infants have two or more symptoms at some point in the first year of life which guidelines say may be caused by cow’s milk allergy, yet the condition only affects one in 100.

Cow’s milk allergy can present with either acute or delayed symptoms. Delayed symptoms are more varied and include gut and skin symptoms, such as posseting (bringing up milk) and vomiting, colic, loose stools or constipation, and flaring of eczema. Many of these symptoms are already known to be common in infants, making delayed cow’s milk allergy difficult to diagnose.

Researchers found that one in four parents reported two or more possible “mild to moderate” symptoms every month. Symptoms were most numerous at three months of age, when all children were fully breastfed and not directly consuming cow’s milk. At six months of age, there was no difference in the number of children with two or more symptoms between those consuming and not consuming cow’s milk. Together, these findings suggest that the majority of symptoms listed in cow’s milk allergy guidelines are common, normal and not caused by cow’s milk allergy.

Dr Rosie Vincent, Honorary Clinical Research Fellow at the Centre for Academic Primary Care, University of Bristol who led the research, said: “Guidelines, designed to help the non-specialist to diagnose cow’s milk allergy in infants may unintentionally medicalise normal infant symptoms and promote over-diagnosis of cow’s milk allergy.”

Senior co-researcher and children’s allergy doctor, Dr Michael Perkin, from the Population Health Research Institute at St George’s, University of London, added: “Our findings come against a background of rising prescription rates for specialist formula for children with cow’s milk allergy, which is completely out of proportion to how common we know the condition is. Parents of young infants are often seen in clinics, worried about a medical cause for their infant’s symptoms such as colic, bringing up milk or loose stools. However, our research confirms that these symptoms are extremely common. In an otherwise healthy infant, an underlying cause is unlikely. Incorrectly attributing these symptoms to cow’s milk allergy is not only unhelpful, but it may also cause harm by discouraging breastfeeding.”

The researchers (from the University of Bristol, St George’s, University of London, Imperial College London, King's College London, and St John’s Institute of Dermatology), used data from the Enquiring About Tolerance study of 1,303 infants aged between three and twelve months, in which parents were asked to record any symptoms their child experienced on a monthly basis. They counted how many infants had cow’s milk allergy symptoms each month, as defined in the international Milk Allergy in Primary Care (iMAP) guideline.

Professor Matthew Ridd, a GP and senior co-researcher at the Centre for Academic Primary Care, University of Bristol, said: “Our study was based on iMAP but our results are likely to apply to other cow’s milk allergy guidelines. Well-meaning guidelines need to be supported by robust data to avoid the harms from over-diagnosis, which may be greater than the damage of delayed diagnoses that they seek to prevent.”

The research was funded by the International Society of Atopic Dermatitis (ISAD) and supported by the National Institute for Health Research. The EAT study was funded by the UK Food Standards Agency.

Paper: Frequency of guideline-defined cow’s milk allergy symptoms in infants: secondary analysis of EAT trial data by Rosie Vincent, Stephanie MacNeill, Tom Mars, Joanna Craven, Kirsty Logan, Carsten Flohr, Gideon Lack, Suzanna Radulovic, Michael Perkin and Matthew Ridd. Published in Clinical and Experimental Allergy. 8 December 2021.

Further information

About the Centre for Academic Primary Care, University of Bristol
The Centre for Academic Primary Care (CAPC) at the University of Bristol is a leading centre for primary care research in the UK, one of nine forming the NIHR School for Primary Care Research. It sits within Bristol Medical School, an internationally recognised centre of excellence for population health research and teaching. Follow us on Twitter: @capcbristol

About the National Institute for Health Research
The mission of the National Institute for Health Research (NIHR) is to improve the health and wealth of the nation through research. We do this by:

Funding high quality, timely research that benefits the NHS, public health and social care;
Investing in world-class expertise, facilities and a skilled delivery workforce to translate discoveries into improved treatments and services;
Partnering with patients, service users, carers and communities, improving the relevance, quality and impact of our research;
Attracting, training and supporting the best researchers to tackle complex health and social care challenges;
Collaborating with other public funders, charities and industry to help shape a cohesive and globally competitive research system;
Funding applied global health research and training to meet the needs of the poorest people in low and middle income countries.

NIHR is funded by the Department of Health and Social Care. Its work in low and middle income countries is principally funded through UK Aid from the UK government.

About St George’s, University of London
St George’s, University of London is the UK’s specialist health university. We are shaping modern health with transformative research, expert teaching and hands-on learning.

Our three research institutes focus on biomedical and scientific discovery, advancing the prevention and treatment of disease in the fields of population health, heart disease and infection - three of the greatest challenges to global health in the 21st century.
We provide a world-class multi-professional health sciences education that equips our graduates to meet today’s healthcare needs through relevant scientific research, clinical excellence, strong interpersonal skills and team-based working. Sharing a clinical environment with a major London teaching hospital, our innovative approach to education results in well-rounded, highly skilled clinicians, scientists, and health and social care professionals.

About International Society of Atopic Dermatitis (ISAD)
The International Society of Atopic Dermatitis (ISAD) was created in 2012 to promote excellence in clinical care, research, education and training in the field of atopic dermatitis and related diseases, to act as a patient advocate and educator in cooperation with lay groups, and to organize the international meeting (Rajka’s Symposium) every two years.