When your body mistakes food as a threat

Food allergies occur when the immune system reacts to something that is usually harmless, such as a peanut, and mistakenly sees it as a threat.

Almost any food can cause an allergic reaction, but the most common food allergy triggers are peanut, egg, cow’s milk, tree nuts, sesame, soy, wheat, fish and other seafood.

Symptoms can include swelling of the face, lips, or eyes, hives (welts) on the skin, vomiting, difficulty breathing, and collapse.

From delayed to early consumption

One of the biggest advances in allergy prevention was recognising the importance of introducing common allergy-causing foods, such as peanuts, to infants at the right time.

In 2008, a study reported that Jewish children in the United Kingdom had higher rates of peanut allergies than Jewish children in Israel. Children in Israel were more likely to eat peanut products in their first year of life.

The authors suggested that this earlier introduction of peanuts in Israeli children’s diets might be preventing peanut allergies.

The Learning Early About Peanut Allergy (LEAP) trial tested this theory in a study that took almost ten years to complete. The researchers randomly assigned 640 infants with eczema or an egg allergy to either:

1. avoid peanuts until age five years, or
2. start eating peanuts by age 11 months.

When the children were five years old, peanut allergies were much less common among those who had started eating peanut products early than among those who had avoided them.

Children who have eczema or egg allergy are more likely to develop a peanut allergy – although peanut allergy can also occur in children without eczema or other food allergies.

What do the guidelines say now?

Following the publication of the LEAP trial findings in 2015, guidelines in the US and Australia were updated to recommend introducing peanut products into the infant diet to reduce the risk of peanut allergy.

Current Australian guidelines recommend introducing all infants to a range of common foods that can cause allergy, including peanuts, in the first year of life. Ideally, this should happen soon after solid foods are introduced.

Foods should be given in a form appropriate for infants, such as smooth peanut butter mixed with purees, and in small amounts to start with.

The new guidelines are a significant change from previous advice. In the 1990s and early 2000s, some guidelines in the US and Australia recommended avoiding peanut products in the first few years of life for children with a family history of allergy.

We now know this did not prevent peanut allergies and, in fact, may have increased the risk.

Around 2008, guidelines in Australia and the US started to change. Although advice to avoid peanut products began to be removed from guidelines, it was not until 2015 that early introduction was explicitly recommended.

What did the US study find?

The US study looked at three cohorts of around 40,000 children aged 0–3 years at three points in 2012–14, 2015–17 and 2017–19.

Peanut allergy prevalence decreased from 0.79% in the 2012-14 cohort to 0.45% in the 2017-19 cohort, a 43% decrease.

However, there are some limitations to the US study.

Food allergies were not directly measured, and instead relied on a diagnosis of food allergy recorded in a medical database.

The way food allergies are diagnosed might change over time with the development of new tests and guidelines, and changing awareness of food allergy. It also means children who didn’t access care for a suspected food allergy weren’t included in the data.

The study also did not look at whether the children with and without a peanut allergy had peanut products introduced into their diet in the same way as the guidelines recommended.

What are we seeing in Australia?

We found that more than eight in ten families introduced peanut products to their infants in the first year of life after the guidelines were introduced, compared with fewer than three in ten before the guidelines.

We are also starting to see a possible decrease in peanut allergy. In one study, peanut allergy decreased from 3.1% to 2.6% after the guidelines, about a 16% reduction.

Unlike the US study, all children were tested for possible peanut allergy using objective tests. This could account for the higher prevalence of peanut allergy in the Australian study.

Other studies have shown hospital admissions for food anaphylaxis, a severe allergic reaction, stopped increasing once these guidelines were released.

It will be important to continue to measure changes in peanut allergy in Australia and internationally to see whether it continues to decrease.

We also know some children will develop a peanut allergy despite introducing peanuts in accordance with the guidelines, while others do not develop an allergy even if they had a delayed introduction.

Our knowledge of how food allergies develop and how they can be prevented continues to evolve. Introducing common allergens in the diet in the first year of life is currently the only strategy to prevent food allergy.

These new findings support the current advice in Australia and may help parents and caregivers feel reassured to continue including common allergy-causing foods in their baby’s diet.

Jennifer Koplin, Evidence and Translation Lead, National Allergy Centre of Excellence; Chief Investigator, Centre of Food Allergy Research; Associate Professor and Group Leader, Childhood Allergy & Epidemiology Group, Child Health Research Centre, The University of Queensland; Desalegn Markos Shifti, Postdoctoral Research Fellow, Child Health Research Centre, Faculty of Medicine, The University of Queensland, and Rachel Peters, Team Leader / Principal Research Fellow, Population Allergy Research Group. Population Health Program Lead, National Allergy Centre of Excellence, Murdoch Children’s Research Institute

This article is republished from The Conversation under a Creative Commons license. Read the original article.