The Learning Early About Peanut allergy (LEAP) study

The Learning Early About Peanut allergy (LEAP) study was a research trial overseen by doctors to understand how to prevent peanut allergy in babies.

What do the findings of the LEAP study mean for Australian babies?

What causes one person to develop a food allergy and not another, is not widely understood.

The LEAP study is a landmark study that has helped researchers and health professionals understand more about preventing peanut allergy in babies considered to be at high risk of developing food allergy.

Babies at high risk of developing peanut allergy were included in the LEAP study. The results showed that the children who started eating peanut before one year of age and kept regularly eating peanut until 5 years of age, had less peanut allergy when compared to a group of children who did not eat peanut until age 5.

This study has helped to reassure parents and carers that introducing peanut before 1 year of age can help prevent peanut allergy from developing, rather than cause it.

Where and when did the LEAP study take place?

The LEAP study took place in England between 2006 and 2014 and the lead senior researcher was a paediatric allergist. The results of the study were published with the title Randomized Trial of Peanut Consumption in Infants at Risk for Peanut Allergy in the New England Journal of Medicine in 2015 with free U.S. Department of Health and Human Services public access.

What prompted the LEAP study?

The idea for the LEAP study was inspired by the low rate of peanut allergies among children in Israel, where babies commonly eat a peanut snack from as early as 4 months of age.

What did the LEAP study involve?

The LEAP study included 640 babies aged between 4 and 11 months who had severe eczema or an allergy to egg, or both.

The babies in the LEAP study were considered to be at high risk of developing peanut allergy. Having severe eczema and/or egg allergy means your baby is more likely to develop a peanut allergy.

Before starting the study, all babies had a test to see if they were already sensitised to peanut. Babies who already had a clinical peanut allergy did not take part in this study.

Being sensitised to peanut was measured by a skin prick test, which is a test where an allergen (e.g. peanut protein) is placed on the skin and then the skin is very lightly pricked to see if a hive or wheal develops. The size of the hive (wheal) is measured and this helps to predict how likely it is that someone will have an allergic reaction if they eat the food.

In the LEAP study, babies with large skin prick tests to peanut were excluded for safety reasons, because there was a higher chance that they already had a peanut allergy.

Of the babies who were skin prick tested and included in the study:

  • 85% of the babies had a negative skin prick test to peanut
  • 15% of the babies had small positive skin prick test to peanut which means their skin reacted, but they were not likely to already have a peanut allergy

All the babies included in the study were divided randomly to one of two groups:

  • Group 1 (avoid peanut) were not given peanut in their diet up to the age of 5
  • Group 2 (eat peanut) were given peanut (an amount roughly equal to 1 teaspoon of peanut butter) in their diet at least 3 times per week until they were 5 years of age

Before starting peanut at home, babies in the “eat peanut” group were given a medically supervised peanut oral food challenge in hospital. During the challenge, the babies were fed precise amounts of peanut, starting with tiny amounts and gradually increasing to normal amounts. They were observed carefully for signs of any allergic reactions to peanut.

When the children enrolled in the LEAP study turned 5, all of the children (including those eating peanut, and those avoiding peanut) undertook a peanut food challenge to find out if they had a peanut allergy.

What did the results of the LEAP study tell us?

1. Starting to eat peanut early (before 1 year of age) and regularly until the age of 5 can reduce the risk of developing peanut allergy.

The children who were fed peanut under 1 year of age and included it regularly in their diets had an 86% reduction in peanut allergy compared to the children who avoided peanut.
Overall, the percentage of children with peanut allergy was higher in the group who had avoided peanuts (17%) compared with the group who had regularly eaten peanuts (3%).

2. Eating peanut early and regularly until the age of 5 years can reduce the development of peanut allergy even in babies who have a small positive skin prick test to peanut.

A 70% reduction in peanut allergy was seen in the group of children with a small positive skin prick test to peanut (and who passed a peanut oral food challenge) when entering the study, compared to children who avoided peanut.
The children who had small positive skin prick tests to peanut had a 1 in 3 chance of developing peanut allergy, but if they regularly ate peanut this was reduced to a 1 in 10 chance.

3. Early introduction to peanut does not prevent peanut allergy in ALL children.

1 in 5 children (20%) in the LEAP study still went on to develop peanut allergy. Further research is needed to understand why. Some babies in the study were not able to eat peanuts during the study because they reacted to the oral food challenge. Some babies had to stop eating peanuts during the study because they began having allergic reactions to peanuts.

4. Early introduction to peanut continues to protect children from peanut allergy

A follow-up study Persistence of Oral Tolerance to Peanut (LEAP-On) showed that early peanut introduction continues to protect children from peanut allergy for 12 months, even if they stop eating peanuts every day. This suggests that protection is long-lasting.

Can the LEAP study results be trusted?

Published studies have been checked by other experts and researchers. The LEAP findings are considered reliable because:

  • it was a randomised controlled trial which means that the study design allowed a fair and unbiased comparison between the ‘eat peanut’ and ‘avoid peanut’ groups
  • the trial was conducted safely and was overseen by experts in the field
  • the number of children in the study was large enough and 98% stayed in the study until the end
  • there was a statistically strong difference between the groups, and
  • the data have been extensively reviewed by experts who were not part of the study

Other key things to know about the LEAP study:

  • The LEAP study was looking at preventing food allergy in children with risk factors for peanut allergy (severe eczema and/or egg allergy).
  • The LEAP study was not looking at treatment for food allergy and that is why infants who were already allergic to peanuts could not be included.
  • More research is needed to see if the results are the same in children from other countries, ethnic backgrounds and those with other risk factors such as milk, wheat or soy allergy.


Du Toit G, Roberts G, Sayre PH, Bahnson HT, Radulovic S, Santos AF, Brough HA, Phippard D, Basting M, Feeney M, Turcanu V, Sever ML, Lorenzo MG, Plaut M, Lack G, LEAP Study Team. Randomized trial of peanut consumption in infants at risk for peanut allergy. N Engl J Med. 2015; 372: 803-13.

Du Toit G, Sayre PH, Roberts G, Sever ML, Lawson K, Bahnson HT, Brough HA, Santos AF, Harris KM, Radulovic S, Basting M, Turcanu V, Plaut M, Lack G, LEAP Study Team. Effect of avoidance on peanut allergy after early peanut consumption. N Engl J Med. 2016; 374; 1435-1443.