TORONTO - Measures to avoid exposing children to food allergens like peanuts in schools and other public places are often based on irrational fears and can lead to over-the-top responses that sensationalize the risk, a medical sociologist suggests.

In fact, says Dr. Nicholas Christakis of Harvard Medical School, in some cases the "gross over-reaction to the magnitude of the threat" has many of the hallmarks of mass psychogenic illness, or mass hysteria.

In an opinion piece published in this week's British Medical Journal, Christakis writes that at his children's school in Boston, parents had to go to the loading dock instead of classrooms to pick up fundraising candy they'd ordered so pupils would not be exposed to possible allergens like nuts.

In another case, "a peanut was spotted on the floor of a school bus, whereupon the bus was evacuated and cleaned ... even though it was full of 10-year-olds who, unlike two-year-olds, could actually be told not to eat food off the floor," he writes.

But Christakis said there is no evidence that any of these extreme restrictions - including banning certain foods from schools - work better than more circumscribed policies or that they justify the disruptions they create.

In the United States, about 2,000 children and adults are hospitalized each year as a result of severe food allergies and about 150 die. Similar statistics for Canada aren't available, but an estimated two per cent of Canadians may be affected by the life-threatening allergies.

In severe cases, exposure can cause anaphylaxis, a potentially fatal reaction that requires immediate treatment with injected epinephrine. Symptoms may include: hives; swelling of the eyes, face, lips, tongue and throat; and difficulty breathing.

"The issue is not whether nut allergies exist or whether they can occasionally be serious," Christakis writes. "Nor is the issue whether reasonable accommodation should be made for the few children who have documented serious allergies."

"The issue is what accounts for the extreme responses to nut allergies and what to do about the responses and the allergies themselves."

Commenting on the BMJ article, allergist Dr. Susan Waserman of McMaster University said it would be unfair to make generalizations about people's responses to allergen avoidance from Christakis's article.

"He's drawing on a very limited experience, when in fact what I see is, sure, not only that segment that may be unduly anxious, unduly restrictive, unduly hysterical, but there are a lot of parents and schools that function and cope extremely well and in a rational manner," Waserman said Tuesday from Hamilton.

She said people often take apparently extreme measures because they haven't been properly educated about the actual risk of kids coming in contact with a food or foods to which they are allergic, including dairy products, soy and shrimp.

Waserman noted there are still many unanswered questions about allergies, such as how much of a certain food is needed to cause a reaction in a particular child and just how vigilant do parents and institutions like schools need to be.

Parents who must contend with the daily fear of their child having a fatal food reaction may want to err on the side of absolute caution, and increasingly schools, communities and prepared food producers are following their lead.

"In certain instances, like for toddlers in nurseries, in places where children do not completely understand about hygiene, about allergy, about sharing food, in those sorts of restricted situations I would say it's probably a good idea to make that environment as safe as possible - meaning to limit the exposure to the foods."

Laurie Harada, executive director of Anaphylaxis Canada, agreed there are some people who appear to over-react to the threat of a child's food allergies, often because they have not been properly educated about the risk.

"I think it's really important to keep things in context," she said. "While I would agree that there is heightened awareness and anxiety and sometimes things are out of perspective, we can show you scores of schools and parents who are dealing quite well with this and walking the balanced line."

"And the reason they're able to do that is they have good information from the get-go or very early on in their child's diagnosis," said Harada, whose 14-year-old son is severely allergic to a number of foods, three of them the most likely to cause a fatal reaction.

"As a parent, you've always got to have your radar up," she said. "When you're putting a child into the school for eight hours a day, they're out of your care and you don't have medical advisers. We have to ask schools to help out."