Why the medical advice on peanut allergies flipped in a generation

alimentation babies peanuts betimes put up facilitate prevent allergies, study suggests

In just 10 years, the science behind preventing peanut allergies in babies appears to have completely flipped, with countries including Canada now recommending giving infants allergenic foods within their first six months of life — rather than total avoidance.

Parents may be hesitant to introduce the foods, given how severe allergic reactions can be — but doctors say there are solid reasons to give the foods early and often.

The shift can be traced back to a pivotal clinical trial led by a doctor in the U.K., who confirmed that early exposure works. In a sign of how the findings continue to reverberate, in February researchers presented their findings based on the younger siblings of the original study's participants, which backs the importance of introducing peanut in the diet at an early age. 

What's more, a recent U.S. Study suggests rates of peanut allergy in children under age three declined 43 per cent over the last several years, after feeding guidelines changed.

"It was a terribly exciting and important discovery," said Dr. Gideon Lack, a professor of pediatric allergy at King's College London and Evelina Children's Hospital, who led the original trial. 

Food allergy rates have plummeted since the 2016 publication of Lack's Learning Early About Peanut Allergy (LEAP) study. It compared peanut allergy cases among infants aged four to 11 months who were at high risk and were randomly assigned to either regularly eat the food in an age appropriate way or to avoid it.

Investigators expected to see a 40 to 50 per cent decline in peanut allergy; instead, they found a 81 per cent reduction. Lack said they celebrated the results with a shot of whiskey.

The team followed the children and found that the protective effect lasted.

A combination of events sparked Lack's initial interest in food allergies, starting in his pediatric training when a teen he was treating died due to an anaphylactic reaction to peanuts.

"A perfectly healthy person can from one moment to the other face a life-threatening or in that particular case fatal outcome," he said. "So that had an influence on me."

As a fellowship trainee in Denver, Colo., Lack worked on mice models of food allergy and saw how the rodents would become allergic after exposing them to egg or peanut protein through the skin. But if the mice were fed the foods at a very young age, they were protected from allergies. 

Later, Lack would regularly present at pediatric and allergy conferences. In 2003 in Israel, he was startled at the response to a question he routinely posed to doctors.

"I asked the audience, how many of you have seen a case of peanut allergy in the last year?" Lack recalled.

"Only two or three people, certainly less than a handful, put up their hand, whereas in the U.K. At the time and most likely in the U.S., every pediatrician or allergist would have put up their arm."

During the same trip, Lack noticed infants in Israel were commonly fed peanut snacks that dissolved in the mouth, a practice that was discouraged in the U.K., Canada and the U.S. At the time.

Lack recognized that the stark difference in peanut allergy rates could be due to many factors, like sunshine or vitamin D levels.

To tease out cause and effect from other factors, Lack randomly assigned 640 infants who were already allergic to eggs, had severe eczema or both, to either eat peanut-containing foods early in life or to avoid the items. Their findings proved conclusively that early introduction prevented allergy.

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Since the LEAP trial proved the beneficial cause and effect relationship of early introduction, Lack spells out the basis of peanut allergy to families and gives parents and caregivers practical tips. 

Lack's suggestions include recipe-like steps:

Parents find it easy, Lack said. As a bonus, sucking comforts the baby. 

Pediatric allergists in Canada also have hands-on answers to questions they often receive from parents. Case in point: What happens if a child has an older sibling with peanut allergies and it's time for the younger one to try it?

"I do have some families where they might do it, for example, when the other, older child is at school, for example, or at daycare or out of the house," said Dr. Douglas Mack, an assistant clinical professor of pediatrics at McMaster University. "I think that's a very reasonable strategy."

Dr. Elissa Abrams, professor in the pediatrics department at the University of Manitoba, recommends parents and caregivers make sure that when kids with allergies are with non-allergic children, they're supervised so there's no chance they eat each other's food.

To test sesame with a baby, her tip is to use tahini mixed in a puree. 

But given that scientists haven't nailed down exactly how regularly and what portion size, once a food is tolerated, Abrams advises keeping it in the rotation. 

"Your immune system needs to be exposed to the allergen on an ongoing basis to remain tolerant to it, to remember not to react to it," Abrams said.

How often? Typically at least twice a week because the immune system needs reinforcement, said Dr. Moshe Ben-Shoshan, a pediatric allergist at Montreal Children's Hospital.

Use nut milks like cashew, Ben-Shoshan suggests, because it avoids the choking hazard and has a lower concentration of the allergic-provoking protein. 

Same for baked forms, like offering the baby a quarter of a muffin mixed with applesauce to introduce eggs. 

Ben-Shoshan also advises parents to avoid putting peanut butter on the baby's skin because it can make eczema flare, which complicates trying to tell if the child is allergic. What parents do during a child's first year is crucial to their anaphylaxis risk for life, while eczema will likely improve with time, he said. 

"Don't hesitate too much to introduce peanuts to the young child," said Ben-Shoshan, who is also an associate professor at McGill University. "Don't let your fear basically paralyze you."

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