The LEAP-On study followed on from the LEAP (Learning Early About Peanut Allergy) study, both led by Professor Gideon Lack, to find out if allergies could be prevented through exposure.
"The aim of our study was to find out whether infants who had consumed peanut in the LEAP study would remain protected against peanut allergy after they stopped eating peanut for 12 months," said Professor Lack.
"It demonstrates that the majority of infants did in fact remain protected and that the protection was long-lasting."
More than 250 children who had completed the original study, and were free of peanut allergies, were instructed to avoid peanuts for 12 months. A similar-size control group continued to eat peanuts regularly. They were then tested to see if they had developed an allergy.
The study found that at 6 years of age, there was no statistically significant increase in allergy after 12 months of avoidance.
There was a 74 per cent relative reduction in the prevalence of peanut allergy in those who ate peanuts compared to those who avoided them.
Peanut allergy develops early in life, is rarely outgrown and there is no cure. The occurrence of peanut allergy has more than doubled in 10 years in the UK.
Michael Walker, a consultant science manager and referee analyst for the Government Chemist programme, welcomed the findings, but added that parents should not attempt to replicate what the studies did by themselves but should follow general guidance. The research was published in the New England Journal of Medicine.