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Does avoidance of peanuts in early life reduce the risk of peanut allergy?

BMJ 2010; 340 doi: https://doi.org/10.1136/bmj.c424 (Published 11 March 2010) Cite this as: BMJ 2010;340:c424
  1. Susannah McLean, clinical research fellow,
  2. Aziz Sheikh, professor of primary care research and development
  1. 1Allergy and Respiratory Research Group, Centre for Population Health Sciences, University of Edinburgh, Edinburgh EH8 9AG
  1. Correspondence to: A Sheikh Aziz.sheikh{at}ed.ac.uk
  • Accepted 16 December 2009

Peanut allergy has increased in frequency and severity such that it is now responsible for considerable morbidity and in some cases mortality. This has led to conflicting policies aimed at reducing the risk of children developing peanut allergy. Expectant women and parents of young children, as well and their clinicians, are therefore often unclear about whether to avoid peanuts.

What is the evidence of uncertainty?

We searched the Cochrane Library and PubMed using a combination of MeSH and free text terms from the inception of these databases to November 2009 to identify relevant systematic reviews and original studies that had investigated the effect of peanut avoidance in pregnancy, in mothers who were lactating, and in the diets of infants, on the risk of subsequently developing peanut allergy. We also searched Google Scholar and online trial registries (ClinicalTrials.gov and Controlled-trials.com) to identify unpublished and ongoing randomised controlled trials.

Changing advice on the role of peanut avoidance

In 1998 the UK government advised that those at “high risk” of developing allergy (that is, those with a family history of allergic problems) may wish to avoid eating peanuts and products that contain peanuts during pregnancy, lactation, and weaning (until infant is aged 3 years).1 Similar advice was issued around the same time in several other countries.2 3

This advice on avoidance of peanuts was based on the findings of epidemiological studies, which suggested that exposure to peanuts during this “critical window” in early life may increase the risk of peanut allergy.4 5 Supportive, potentially more compelling, evidence came from the early randomised controlled trials of avoidance of dietary allergens (including peanut) during pregnancy and/or early childhood; these trials found significant reductions in the risk of children developing allergic disease when dietary allergens had been avoided.6 7

This general agreement on the importance of avoiding peanuts in high risk families in early life has recently been challenged, however, by concerns that avoiding peanuts during this critical immunological window may in fact increase the risk of food allergy.8 9 This has led to the Department of Health and the UK Food Standards Agency recently issuing revised advice (box).10 New Zealand’s Ministry of Health and the American Association of Paediatrics have also updated their advice.3 11

Summary of revised advice on peanut avoidance from the Department of Health and the Food Standards Agency10

During pregnancy and while breast feeding
  • If mothers wish to eat peanuts or foods containing peanuts during pregnancy or breast feeding then they can do so as part of a healthy balanced diet, irrespective of whether their child has a family history of allergies

When introducing peanut into a child’s diet
  • All mothers should try to exclusively breastfeed their baby for the first 6 months of life. If mothers choose to start giving their baby solid foods before age 6 months, they should not introduce peanuts or other allergenic foods (such as other nuts, seeds, milk, eggs, wheat, fish, or shellfish) before this time, and when they do, these foods should be introduced one at a time so that they can spot any allergic reaction

Additional advice
  • Where a child already has another kind of allergy (such as diagnosed eczema or a diagnosed allergy to foods other than peanut), or if there is a history of allergy in the child’s immediate family (parents, siblings) then mothers should talk to their general practitioner, health visitor, or medical allergy specialist before giving peanut to the child for the first time because these children are at higher risk of developing peanut allergy

Why are there concerns about peanut avoidance?

Four key arguments have been raised. Firstly, evidence from randomised controlled trials on the effectiveness of dietary restriction during pregnancy and lactation is conflicting. A Cochrane systematic review concluded that avoidance of foods during pregnancy was unlikely to be effective and that no compelling evidence existed for mothers to avoid allergens while lactating.12

Secondly, an epidemiological study conducted several years after the introduction of the initial UK advice failed to show the anticipated reduction in the prevalence of peanut allergy.13

Thirdly, evidence exists that the original UK advice was not clearly communicated to the target population of high risk families, and this shortcoming resulted in many cases of blanket avoidance of peanuts, even in low risk families.14

Finally, and most fundamentally, evidence is increasing that oral exposure to allergens such as peanuts in early life may be important for inducing immunological tolerance to these foods. Particularly important in this respect has been an epidemiological study that found that the prevalence of peanut allergy was 10-fold lower in Jewish people living in Israel—where peanut butter is used in the weaning food “Bamba”—than in London based Jewish families, who had less frequent exposure to products containing peanut.15

Is ongoing research likely to provide relevant evidence?

Two ongoing randomised controlled trials, scheduled to report in 2013-5, should begin to provide clarity on whether or not to expose infants to peanuts in early life. The EAT trial is comparing infants introduced to allergenic foods—including peanuts—from the age of 3 months with infants in a control group who will avoid foods containing these allergens until aged 6 months.16 The main outcome for this trial is the prevalence of IgE mediated allergy to these foods by the age of 3 years.

The related LEAP trial in high risk infants aged 4-11 months is comparing those being fed at least 6 g of peanut protein a week with those in a control group whose diet excludes peanuts. The main outcome of interest is the proportion of children with peanut allergy at age 60 months.17

What should we do in the light of the uncertainty?

At present, the soundest position is to advise all pregnant women who are not allergic to peanuts, irrespective of whether or not there is a family history of allergy, that there is no evidence of danger from eating peanuts. Breast feeding should be encouraged, although no clear evidence exists that avoiding peanuts during lactation will reduce the risk of peanut allergy. It is important to explain that currently we do not know the best time for children to be exposed to peanuts. In general, however, foods that are potentially allergenic are best first introduced one at a time, beginning with small quantities, when the child is otherwise well. If mothers are anxious, discussions with their general practitioner may prove useful, with testing for sensitisation to peanut if necessary.

Whole peanuts present a choking danger and should therefore, irrespective of any concerns about allergy, be avoided until children are at least 3 years old.

Notes

Cite this as: BMJ 2010;340:c424

Footnotes

  • This is a series of occasional articles that highlights areas of practice where management lacks convincing supporting evidence. The series advisers are David Tovey, editor in chief, the Cochrane Library, and Charles Young, editor of BMJ Clinical Evidence and editor in chief, BMJ Point of Care.” We welcome any suggestions for future articles (uncertainties.bmj{at}bmjgroup.com).

  • We thank the reviewers and editors for their helpful comments on an earlier version of this article.

  • Contributors: AS conceived this article, SMcL drafted the paper, and AS commented on the draft. SMcL is the guarantor.

  • Funding: No special funding.

  • Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare that (1) both authors have support from the University of Edinburgh for the submitted work; (2) both authors have no relationships with companies that might have an interest in the submitted work in the previous three years; (3) their spouses, partners, or children have no financial relationships that may be relevant to the submitted work; and (4) SMcL has no non-financial interests that may be relevant to the submitted work, and AS has a child with a food allergy.

  • Provenance and peer review: Not commissioned; externally peer reviewed.

References

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