Anne McDonah's first three children were allergy-free. So, even though some pediatricians recommend holding off on peanuts, Ms. McDonah wasn't overly worried about peanut exposure with her fourth baby.
But when 10-month-old Olivia took a bite of her sister's peanut butter sandwich in August, within seconds, nasty red hives broke out over her body. She was rushed to an emergency room and a subsequent allergy test turned up positive.
"I was aware of peanut allergies," said Ms. McDonah of Truro, N.S., though she'd "never dreamed of it" in her own kids.
For the McDonahs, Olivia's reaction was an alarming introduction to a vexing and poorly understood allergy that parents across Canada are facing in greater numbers.
And more babies as young as Olivia - and even younger - are showing up at emergency departments and clinics with their first allergic reaction, according to a new study out of the United States.
Despite some suggestions from health authorities that delaying peanut exposure might forestall the development of allergies, parents appear to be giving the nuts to their babies earlier.
The median age of first peanut-allergy reactions has dropped to 14 months from 21 months over the past decade, researchers found in the study, published yesterday in the American Academy of Pediatrics' journal Pediatrics. The median age at which the allergic child was first exposed to peanuts has dropped to 12 months from 19 months.
Like much in the world of peanut allergies, the reason for the allergy showing up earlier remains a mystery, says lead author Todd Green, an allergist and immunologist at Children's Hospital of Pittsburgh at the University of Pittsburgh Medical Center and assistant professor of pediatrics at the university.
The research doesn't offer a definitive explanation for the trend, which experts say appears to be the case in Canada as well. But it adds to a growing body of clues that may eventually pinpoint the cause of the explosive growth in food allergies.
Medical experts estimate 1.5 per cent of Canadian children suffer from peanut allergy, and peanut-free snacks and peanut-free schools are becoming less of an option for all parents. Allergy rates rise to 5 to 6 per cent in children for all foods. In the past five to 10 years, food allergy rates have doubled, says allergist and clinical immunologist Susan Waserman of Hamilton's McMaster University.
The new results bore out a hunch that researchers had: "We felt like the kids we were seeing in our clinics were showing up at younger ages," Dr. Green says. The researchers compared the medical data of peanut-allergic patients at the Duke University pediatric allergy and immunology clinic between 2000 and 2006 with those of a similar population between 1995 and 1997.
Other researchers are working to determine exactly how tolerances to peanuts and other foods develop during particular windows of child development. It may be an intricate calculus involving both age and the quantities consumed, some say. It could mean that more peanuts, ingested at certain ages, may be better than none.
In kids considered high risk (one with parents or siblings with any allergy or with asthma), the Canadian Paediatric Society and the American Academy of Pediatrics recommend delaying the introduction of peanuts, tree nuts (pecans or walnuts) or shellfish until age 3. Some pediatricians recommend delaying peanut exposure until the age of 1 in children who are not high risk.
But the advice to hold off on the peanuts could actually be making the problem worse, Dr. Waserman says.
It's likely many children who avoid peanuts are still, in fact, exposed to trace amounts, she says. This may, in turn, "tickle the immune system" just enough to turn on an allergy. "The advice we're giving to people to avoid may in fact be contributing to a worsening problem," she says.
Researchers still don't know much about why anyone is allergic to peanuts. Various theories are being explored, from the types of peanuts we eat in North America - roasted, not boiled - to the "hygiene hypothesis," which suggests that in our relatively clean environments, our immune systems aren't busy fighting as many infections as they once were, so they, in effect, create allergies where once there were none.
Another potential explanation for the drop in age could also be that public awareness campaigns have made parents more vigilant about the first signs of a peanut allergy and they are seeking treatment earlier.
Despite the conflicting evidence, experts including Dr. Green say until we know more, delaying introduction of peanuts into a child's diet is a good idea, if only for one good reason. "It tends to be easier in older kids because they can tell you if their mouth feels funny right away," he says. "Babies just can't tell you."
Likewise, until allergists are able to individualize their diagnoses, there's no way of knowing who is at risk of a mild or a severe reaction at any age.
That's the conundrum for parents such as Jeff and Amanda Smith, who have to approach their daughter Madeleine's peanut allergy as life-threatening. The Kitsilano, B.C., couple learned that Madeleine was allergic last Boxing Day when she was 18 months old and a snack resulted in swollen lips and hives.
Like little Olivia at the opposite end of the country, Madeleine never leaves the house without an injectable dose of epinephrine, which reverses the allergic reaction.
Still, because there is an unknowable risk of severe anaphylactic shock, the Smiths have given up activities such as camping trips.
"It's all or nothing," Mr. Smith says. "She's either totally fine or it's an emergency."
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Nut myths
The advocacy group Anaphylaxis Canada conducted a survey on 32 recent food-induced anaphylaxis deaths in Ontario. They found
a number of myths to bust.
Myth: People who experience mild reactions to peanuts, tree nuts or shrimp will probably
never have a fatal reaction.
Truth:
Six of 32 people had experienced "mild" reactions in the past.
Five of 30 had never reported their symptoms to a physician.
Myth: The first sign of food
allergy is often a fatal allergic
reaction.
Truth: As far as they could tell, at least 10 of 32 people had shown some prior reactivity to their allergen. Two of six people who died from ingestion of tree nuts knew that they were allergic to peanut but had not been
tested for tree nuts.
Myth: Simply the smell of
peanut butter can trigger
a severe or even fatal reaction. Truth: All fatalities followed
actual ingestion of food.
There were also two examples
of a peanut-butter-contaminated knife.
Source: A Study of 32
Food-Induced Anaphylaxis
Deaths in Ontario; 1986-2000,
by Anaphylaxis Canada.
Available at Anaphylaxis.org
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