Persistence of Oral Tolerance to Peanut (LEAP-ON)

Principal Investigator

Gideon Lack, MD | Evelina Children's Hospital | London, UK


Evelina Children's Hospital | London, UK

Study Code


Study Status



Food allergies and peanut allergy (PA) are becoming increasingly common conditions and are now an important public health concern. Dietary avoidance of peanut in early life has been recommended in many countries; however, there is evidence that the prevalence of PA is decreased in countries where children are fed peanut beginning at an early age. The primary aim of the LEAP Study, initiated in 2006, is to test the hypothesis that early peanut consumption may prevent the development of PA.

The LEAP study showed that of the children who avoided peanut, 17% developed peanut allergy by the age of 5 years. Remarkably, only 3% of the children who were randomized to eating the peanut snack developed allergy by age 5. Therefore, in high-risk infants, sustained consumption of peanut beginning in the first 11 months of life was highly effective in preventing the development of peanut allergy. However, the question remains whether continued consumption of peanuts throughout life is required in order to be able to safely eat peanuts without reacting. The LEAP-On Study addressed this question.

The primary objective of the LEAP-On Study was to evaluate persistent tolerance to peanut by assessing the effect of 12 months of cessation of peanut consumption after 5 years of consumption versus continued avoidance of peanut in the LEAP study population.  Infants who have eaten peanut up to 5 years of age as part of the LEAP study were asked to stop eating peanuts for one year, and those who were avoiding peanuts for 5 years continued to avoid eating peanuts.

After 12 months of peanut avoidance, only 4.8% of the original peanut consumers were found to be allergic, compared to 18.6% of the original peanut avoiders, a highly significant difference. This is an indication that eating peanuts early in infancy is an effective and safe strategy to prevent PA in the long term.

Additionally, collection and analysis of blood specimens from these children will provide the opportunity to understand how the body's immune system is able to recognize and tolerate innocuous food proteins such as peanut. Understanding these mechanisms may help develop effective treatments for PA, which are currently lacking.