Testing for food allergies in children with eczema

This aricle was first published in the June 2019 edition of National Eczema Society’s membership magazine, Exchange.

While parents are often concerned that food allergies may be causing their child’s eczema, this is often not the case. Yet uncertainty surrounds the role of diet in managing eczema. Here, Dr Matthew Ridd and colleagues explain a new study (‘TEST’ – Trial of Eczema allergy Screening Tests) that’s looking to see how useful it is to do routine food allergy tests in children with eczema.

Many parents worry that a food allergy is a cause of their child’s eczema. Such parental concern, together with uncertainty among clinicians about the role of food allergy in eczema, are a barrier to effective treatment. Up to 70% of parents make significant modifications to their child’s diet, usually without professional advice, even if the child has only mild eczema.

While food allergy is associated with eczema, it is not the underlying cause of most children’s day-to-day dry, itchy and red skin. If a food causes a sudden reaction, such as wheezing, vomiting, diarrhoea or rash, then parents should avoid giving this to their children, and seek medical and dietary advice.

However, for children who seemingly “just” have eczema, we don’t know whether avoiding certain foods makes any difference to eczema symptoms. In this situation, parents commonly ask about taking allergy tests. However, these are imperfect, can sometimes give misleading information, and experts disagree about their value.

Some parents take matters into their own hands and buy self-test allergy kits on the high street or through the Internet, which are neither validated nor recommended by experts.

A review published in 2008 found no evidence of benefit for managing eczema by excluding particular foods from the diets of adults or children with no clinically suspected food allergies. However, one trial suggested that infants with eczema who have a positive allergy test for egg may benefit from an egg-free diet.

While this suggests that test-guided, dietary management of eczema may be worthwhile, better-designed and conducted trials are needed. Those with eczema and their doctors agree that this is a research priority.

In 2013, the James Lind Alliance Eczema Priority Setting Partnership identi ed the following research questions:

  • “What role might food allergy tests play in treating eczema?”
  • “What is the role of [exclusion] diets in treating eczema?”

These are hot topics because of recent evidence (e.g. the LEAP and EAT studies) showing that earlier introduction of foods that sometimes cause allergies may actually help to prevent sudden, severe (anaphylactic) reactions.

However, when parents consult their GP about their child’s eczema many uncertainties remain regarding food allergy testing and the relationship between possible allergy symptoms, allergy test results, subsequent dietary advice and how parents will act on this, both in terms of their child’s diet and other treatments.

To help resolve these issues, “TEST” is a new study to see how useful it would be to do routine food allergy tests for children who have been diagnosed with eczema. We are conducting an initial feasibility study to find out how best to design a second, much larger trial that people will want to take part in, and that gives the answers that parents and clinicians need.

Around 80 children with eczema are taking part in the feasibility study. Half are receiving “usual care”, while the others are also being asked extra questions and offered skin prick tests for allergies. The tests involve using a very fine needle (which gives a light pricking sensation) to put small drops of six common allergy-causing foods (hen’s egg, peanut, cow’s milk, cashew, codfish and wheat) into the skin and noting any local skin reaction (swelling). If the results are unclear, we may recommend that some children have repeat tests or visit their local hospital to be observed eating some of the food(s).

Depending on what the questionnaires and tests show, we are advising parents whether an exclusion diet might be worth trying to help their child’s eczema. We are following everyone up for 6 months and will be interviewing some parents and GPs to nd out what they think about the tests and the study itself.

At the end of this project, we will know how well a bigger study like this would work. We will also have a better understanding of what parents and GPs think about food allergies and tests in children with eczema. We expect to publish our findings in early 2020, and if we show that a larger study would be feasible, we will apply for funding to do such a trial to help us understand whether routine allergy testing in young children with eczema is helpful.

About the authors

Dr Matthew Ridd is a GP and Reader in Primary Health Care, University of Bristol.

Dr Robert Boyle is a Paediatric Allergist and Reader in Paediatric Allergy at St Mary’s Hospital, Imperial College London.

Dr Julie Clayton is a Coordinator for Patient and Public Involvement in Research at the Centre for Academic Primary Care (www.bristol.ac.uk/ capc), University of Bristol.

This article was reviewed by Catherine Gray and Jo McMeechan, who are parents of children with eczema, with and without food allergies, and are members of the research team.

Further information and acknowledgements

See the study website www.bristol.ac.uk/ eczema-allergy-study and Twitter feed @eczema_allergy or email test-study@bristol. ac.uk

The study is funded by National Institute for Health Research (NIHR) School for Primary Care Research (project 383). The views expressed in this publication are those of the authors and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health and Social Care.

This article was first published in the June 2019 edition of the National Eczema Society members’ magazine, Exchange.