Peanut allergies were substantially less likely to develop among children at high risk if they ate snacks containing peanut butter early in life compared with those who stayed clear of it, a large new randomized trial suggests.

The prevalence of peanut allergies has grown in North America, Western Europe and Australia to between 1.4 to three per cent and is on the rise in African and Asian countries. Peanut allergies can cause reactions ranging from hives and abdominal pain to life-threatening anaphylaxis.

Doctors have looked to randomized trials for guidance on when the best time is to introduce peanuts. Monday’s issue of the New England Journal of Medicine provides some answers.

"Our findings showed that early, sustained consumption of peanut products was associated with a substantial and significant decrease in the development of peanut allergy in high-risk infants," pediatric allergy Prof. Gideon Lack of King's College London and his co-authors concluded.

The study included 640 infants with severe eczema, egg allergy or both, which put them at high risk of developing a peanut allergy. They had standard skin-prick tests to check for peanut sensitivity and were then assigned to eat a peanut-containing snack at least three times a week or to avoid peanuts until five years of age.

Eating snacks with peanuts was associated with an 86 per cent reduction in peanut allergies at 60 months among those who tested negative on the peanut skin-prick test initially — 13.7 per cent versus 1.9 per cent.

'She started with redness and swelling and I knew at that point something was terribly wrong.' - Christina Fiorini

Dr. Hugh Sampson of the Icahn School of Medicine at Mount Sinai in New York wrote a journal editorial published with the study. Sampson said he considers the study to be a landmark because it answers the question of cause and effect and could lead to a significant decrease in peanut allergies in the population.

Questions remain, Sampson said, such as:

  • Will lesser amounts of peanut suffice?
  • Will tolerance last if children stop consuming peanuts regularly?
  • Can the findings be applied to other allergy-provoking foods, such as milk, eggs and tree nuts?
  • What do the findings mean for children who aren't at high risk?

Dr. Susan Waserman, an allergist and immunology at McMaster University in Hamilton, is conducting a similar clinical trial in children aged five to 10, which also includes a placebo.

Peanut feeding advice

"I think that we've had some idea about this for the past few years when all the avoidance we've been recommending seemed to make no difference. This study now nails it down I think in quite an impressive fashion that early introduction appears to be helpful," Waserman said.

"If I do have a family where this is a child who is at high risk because of eczema, because of another sibling with peanut allergy, because of allergic parents my advice would be to introduce peanut early."

While the discovery has the potential to become widespread, Waserman cautioned people to speak with their doctor first.

Christina Fiorini of Woodbridge, Ont., has a nine-year-old daughter, Katarina, with an anaphylactic allergy to peanuts, lobster, crab and shrimp. Fiorini discovered the peanut allergy when Katarina was two, and came into contact with peanut butter.

"She started with redness and swelling and I knew at that point something was terribly wrong. I went for the Benadryl as I called 911," Fiorini recalled.

"When the ambulance care workers got there, she had blown up. She had swelled significantly. The redness was out of control."

While Fiorini thinks it’s best to expose a child early on, fears of that day still haunt her and make her reluctant to expose her sons, Christian, 7, and Leo, 19 months, to peanuts.

"We see Christian and Katarina's allergist and asthma specialist regularly and we always have this conversation. I always leave the office saying 'Yes, I'm going to.'" It hasn't happened yet.

The new findings were also presented Monday at the annual meeting of the American Academy of Allergy, Asthma and Immunology. At the meeting, Sampson presented his results on using a patch to deliver small doses of peanut protein to increase tolerance in people aged six to 55.

Lack's study was funded by U.S. National Institute of Allergy and Infectious Diseases, Food Allergy and Research Education, Medical Research Council and Asthma U.K., U.K. Department of Health, National Peanut Board and the United Kingdom’s Food Standards Agency.

With files from CBC's Thomas Daigle