PEANUT allergy is one of the most common food allergies affecting Australian children, with around 3% of infants and young children currently living with a peanut allergy (here and here). Individuals living with peanut allergy are at risk of accidental reactions, which can be severe and occasionally life-threatening. The risk of accidental exposure and vigilance required to maintain avoidance has a significant impact on the quality of life of children living with peanut allergy and their families (here and here).
Peanut allergy is often lifelong. Less than 30% of infants with peanut allergy will outgrow their allergy by school age. Peanut allergy often presents in infancy, with reactions commonly occurring on the first introduction of peanut into the infant diet, although later-onset peanut allergy has also been reported.
Why does timing of introduction of peanut into the infant diet matter?
There is convincing evidence from a high quality randomised controlled trial (the LEAP trial) that introducing peanut into the infant diet in the first year of life reduces the risk of developing peanut allergy. However, this trial was conducted in a select group of infants at high risk of developing peanut allergy, that is, infants with early-onset moderately severe eczema and/or pre-existing egg allergy, who underwent screening for pre-existing peanut allergy before inclusion in the study.
The strict entry criteria into this trial may limit its generalisability to other settings and is not clear whether early introduction can prevent peanut allergy in the general population, including those at low risk of developing peanut allergy. In our previous population-based food allergy study, nearly a quarter of peanut allergy developed in infants who are not within the “high risk of peanut allergy” definition used in the above LEAP trial.
What are the current Australian guidelines around timing of peanut introduction?
In Australia, infant feeding guidelines for allergy prevention were updated in 2016 in response to the emerging research in this area. In 2015, our Centre for Food and Allergy Research held an Australian Infant Feeding Summit to appraise the new evidence and developed revised recommendations for infant feeding. Three recommendations resulted from the national consensus between experts, stakeholders and researchers. These were:
- introduce solid foods around 6 months of age, but not before 4 months;
- introduce allergenic foods including peanut butter and cooked egg in the first year of life;
- hydrolysed infant formula is not recommended for the prevention of allergic disease.
The consensus aimed to provide consistency between different Australian guidelines to ensure clear consumer advice while balancing the need for food allergy prevention with other nutritional priorities, including the known benefits of breastfeeding. These recommendations were subsequently incorporated into the Australasian Society of Clinical Immunology and Allergy’s infant feeding guidelines.
How have infant feeding guidelines changed over the past few decades and what has been the impact of these guidelines?
Allergy prevention guidelines have undergone three major changes since the 1990s. Initially, guidelines recommended dietary allergen avoidance in infancy because it was thought that this may prevent food allergy. This advice was removed around 2008 as evidence emerged that consuming allergens was important to induce tolerance, although allergen ingestion was not yet actively encouraged. It was only from 2016 that the strong recommendation to introduce allergens in the first year of life to prevent allergy was incorporated in Australian and international guidelines.
Given this major shift in approach, it would not have been surprising if parents and health care providers were reluctant to follow the latest advice. Early surveys in the United States noted low willingness to implement early allergen introduction among both parents and health care providers, adding to these concerns.
We also showed in a large population-based Australian cohort that removal of advice to delay allergen introduction in 2008 was followed by only a small shift towards earlier introduction of peanut, with most parents continuing to avoid giving peanut products to infants in the first year of life.
Despite these early concerns, we demonstrated high uptake of early peanut introduction among Australia infants after the 2016 guideline changes. We conducted two large population-based studies in Melbourne, Australia, 10 years apart, including a total of over 7000 participants, using the same sampling frame and methods to assess changes in practices around egg and peanut introduction to infants as well as food allergy outcomes.
We demonstrated a striking shift towards earlier peanut introduction, with a threefold increase in the proportion of infants consuming peanut before age 1 year in 2018–2019, compared with 2007–2011, from 28% to 88%. Infants at high risk of peanut allergy, namely those with early-onset eczema, had similarly high rates of early peanut introduction, providing reassurance that these guidelines are being taken up by the group who are likely to benefit the most from early peanut introduction. These findings were supported by a national survey of 1940 parents, which showed similarly high rates of peanut introduction in infants by age 12 months (86%).
Although the community responded well to the new infant feeding guidelines, the more important question was whether this had the desired effect of reducing the prevalence of peanut allergy. We compared the impact of earlier peanut introduction on the prevalence of peanut allergy using data from these same two population-based studies. Despite the large increase in early peanut introduction, we found only a relatively small reduction in peanut allergy prevalence, from 3.1% to 2.6%, highlighting that more needs to be done to prevent peanut allergy in the general population.
However, it should be noted that, as expected, earlier peanut introduction was still associated with a reduction in the risk of peanut allergy, and that the reduction in peanut allergy prevalence appeared somewhat more promising in infants with eczema.
Raising awareness of guidelines and changing practice – do we need to do more?
Timely introduction of peanut into the infant diet remains the only evidence-based strategy to reduce the risk of developing a peanut allergy. It remains important that all parents are made aware of current advice and are confident in introducing peanut to their infants. This is particularly the case for those infants who are at higher risk of developing peanut allergy because they have eczema, particularly eczema that starts in early infancy or is severe.
Raising awareness of infant feeding guidelines in culturally and linguistically diverse populations is also critical. We showed that parents who were born in Asia were less likely to introduce peanut to their infants in the first year of life, and infants born to Asian-born parents are at higher risk of developing food allergy (here and here). The Nip Bub project, an initiative of the National Allergy Strategy, was developed to disseminate infant feeding guidelines to parents, GPs and maternal child health nurses, and has tips for introducing allergenic foods to infants, with development of resources for culturally and linguistically diverse populations currently underway.
It is also possible that more regular consumption of allergenic foods once they are introduced may help to prevent food allergy, although evidence for this is limited. Current recommendations suggest that once introduced, these foods should continue to be included in the baby’s diet at least twice a week.
It is also important that parents are reminded to introduce peanut products in a form that is safe for infants to consume. Whole nuts are dangerous for young babies and toddlers because they present a choking hazard. The frequency of nut inhalation in Melbourne increased over the past decade, although this was still a rare occurrence.
What else needs to be done to prevent peanut allergy?
Current evidence indicates that more will need to be done to prevent the development of peanut allergy, even if optimal introduction of allergenic foods to infants in the first year of life can be implemented for all infants. Some infants will develop peanut allergy despite early peanut introduction, and some infants will develop peanut allergy before they are developmentally ready for introduction of peanut into their diet.
As a result, other strategies for food allergy prevention are currently under investigation. Several are being tested in large-scale randomised controlled trials in Australia, including the role of maternal consumption of allergenic foods (egg and peanut) during pregnancy and breastfeeding and a trial of infant vitamin D supplementation for allergy prevention.
Results from these trials are expected in the next 2–3 years. Continuing to recommend introduction of peanut in the first year of life is critical to reducing the population prevalence of peanut allergy, as is developing additional prevention strategies for infants who fail to benefit from early peanut introduction, and we eagerly await the results of these and other trials of novel food allergy prevention strategies.
Associate Professor Jennifer Koplin is head of the Childhood Allergy group at the University of Queensland Child Health Research Centre and an honorary fellow at the Murdoch Children’s Research Institute.
Associate Professor Rachel Peters leads the epidemiology stream of the Population Allergy research group at the Murdoch Children’s Research Institute. Her research program focuses on the epidemiology of allergic diseases.
Dr Victoria Soriano is a postdoctoral researcher at the Murdoch Children’s Research Institute, having recently completed her PhD in epidemiology at the University of Melbourne.
The statements or opinions expressed in this article reflect the views of the authors and do not necessarily represent the official policy of the AMA, the MJA or InSight+ unless so stated.
Subscribe to the free InSight+ weekly newsletter here. It is available to all readers, not just registered medical practitioners.
If you would like to submit an article for consideration, send a Word version to firstname.lastname@example.org.