All about allergies

Some families hand down precious heirlooms. Mine bestows a body primed to gush tears and mucus at a sniff of pollen, or erupt in rash at the touch of plants or perfume. We’re in good company — as many as one in two Canadians suffer from allergies, according to Susan Waserman, an allergist and clinical immunologist and associate professor of medicine at McMaster University in Hamilton. So what exactly is an allergy? And what’s new in testing and treatment? If you’re itching for answers, read on.

What’s an allergy?

An allergy stems from a communications glitch in the immune system — the police force that protects the body against parasites and disease. For some unknown reason, the dispatcher issues an all-points bulletin for a suspect considered armed and dangerous. But it’s a case of mistaken identity: The suspect (a.k.a. allergen) is a normally harmless substance, say, ragweed pollen, but the officers attack as if it were a violent offender, triggering symptoms like runny eyes. Trouble is, after the supposed felon has been run out of town, the SWAT team stays on red alert — each time it spots the allergen again, the battle begins anew.

Doctors describe people whose immune systems are prone to making this kind of error as atopic. This tendency expresses itself in different ways. “Allergy can result in a number of different diseases,” Waserman notes. It may be asthma, triggered by allergy, or hay fever or eczema.

How do I know if my child has an allergy?

You will need to get her tested, but here are three clues:

• You or your partner has a family history of allergies. “Even though non-allergic parents can have allergic kids, if parents have allergies, there’s a two- to threefold risk of having an allergic child,” observes Zave Chad, an allergist and clinical immunologist and chair of the Canadian Paediatric Society’s Allergy Section.

• Your child has a history of eczema. “Kids who have allergies often start life off with eczema — dry, itchy skin,” Chad explains.

• Certain symptoms (itchy skin or hives; swelling; itchy eyes, nose or throat; watery eyes; sneezing; runny or blocked nose) hint at allergy. Occasionally, a food allergy might make itself known via vomiting, diarrhea or even a child’s refusal to eat a forkful of the offending stuff.

How many kids have allergies?

Numbers are probably most reliable for food allergies. John Dean, head of the allergy clinic at BC Children’s Hospital in Vancouver, says, “Around 60% children under the age of 3 or 4 have food allergies; when you get to the age of 5, the figure falls down to 1 to 2%.” According to Dean, “up to one-third of parents of young children think their child has a food allergy,” so these numbers should be reassuring to all those worried moms and dads. The hay fever picture is fuzzier, but there’s no question it’s far more common. Our experts estimate 20 to 400f kids are affected:

6% 

of kids under age 3 or 4 have food allergies, but most outgrow them by school age

10%

of children get eczema, which usually disappears in late childhood. Half of those affected, though, develop another allergic disorder later in life

15%

 of kids have asthma (more than double the adult rate). About half outgrow it by adolescence

Why do so many more people have allergies than in the past?

Experts aren’t sure, though there are many suspects (pollution, dust mites, chemicals in our airtight homes, our diets, etc.). The theory backed by the most evidence goes like this: Kids who aren’t exposed to a lot of parasites, bacteria and endotoxins (bacteria found near animals) miss out on “target practice” — without it, their immune systems are more prone to the errors that cause allergies. This may be why rates are highest in countries with good sanitation, and city kids are more allergy-prone than their country cousins. This “hygiene hypothesis” was bolstered recently by an American study that found kids who carried H. pylori (the bacterium linked with ulcers) were less likely to have asthma, wheezing, nasal allergies or skin rash than H. pylori-free children.

There’s also preliminary evidence the sunshine vitamin could play a role. In a recent study, low blood levels of vitamin D in pregnant women were linked with an increased risk of having children who develop asthma. This could partially explain why asthma is so prevalent in countries like Canada, where the sun’s rays are weaker in winter.

What’s the latest in allergy treatment?

There’s an exciting new twist on old-fashioned immunotherapy — the allergy shots that desensitize someone to a specific allergen through repeated exposure to it in tiny amounts. Scientists have come up with allergen-containing drops and pills that go under the tongue, a treatment that should soon be coming to Canada, according to Amin Kanani, an allergist and clinical immunologist at Vancouver’s St. Paul’s Hospital and clinical assistant professor at the University of British Columbia. Although “it doesn’t work as well as injections,” says Kanani, the under-the-tongue option is more palatable for many kids and less likely to trigger a reaction, so it can be given at home instead of at the doctor’s office.

Are allergies and asthma related?

Asthma is a chronic disease that makes it hard to breathe. About 50 to 850f cases are thought to be allergy-related. However, some kids’ symptoms flare up primarily when they catch viral infections like colds, and it’s these children who are most likely to grow out of their wheezing by age 10, says Brian Lyttle, a paediatric respirologist and assistant professor at the University of Western Ontario in London.

When should I suspect my child has asthma?

Asthma is more common in allergic families and in kids with a history of eczema. A persistent pattern of coughing or wheezing also points to the condition. For example, some kids wheeze when they exercise or breathe cold air; others hack their way through every night of ragweed season. Frequent colds that drag on longer than the usual two weeks are another clue. Asthma can also disguise itself as recurrent bouts of bronchitis, pneumonia or croup.

Is it true asthma is on the rise?

The last time Statistics Canada collected data in young children (1998/99), 9.10f kids aged 9 and under, and 11.90f those 10 to 14, had been diagnosed with asthma (but it’s estimated the numbers are higher since mild disease doesn’t always get picked up). Since these numbers are nearly 10 years old, we don’t know if asthma is currently on the rise, but we do know asthma rates in Canadian kids climbed from an estimated 2.5 0n 1978 to 11.2% in 1995. The same factors suspected in allergies may be to blame here too.

What’s new in asthma testing and treatment?

Asthma medications are becoming more effective so it’s often possible to eliminate symptoms that interfere with normal activities. Doctors also have a few more medicines to choose from, including a pill, and an injectable drug that works well for very severe allergic asthma (though the latter is very expensive).

There’s also a new development in asthma diagnosis and monitoring. A test that measures the amount of nitric oxide gas that a person exhales — used as a research tool since the 1990s — is beginning to move into doctor’s offices. (Nitric oxide is given off by a type of cell that’s involved in allergic reactions.) “It’s similar to spirometry, which measures ‘airway calibre,’” explains Lyttle.

Tell me about anaphylaxis. How common is it?

“Anaphylaxis is basically a very serious allergic reaction,” Chad explains. It usually comes on very rapidly and affects multiple body systems. Symptoms vary widely and can include progressive hives, dizziness, difficulty breathing, abdominal pain and dangerous drops in blood pressure. The allergens most apt to cause these reactions are insect stings, latex and foods (peanuts, tree nuts, eggs, milk, etc.). According to Anaphylaxis Canada, 1 to 20% of Canadians are at risk.

Is there anything a parent can do to protect a child from allergic diseases such as peanut allergy?

Staying smoke-free during pregnancy and beyond reduces the risk of asthma, which is often a contributing factor in anaphylaxis deaths. Otherwise, there’s next to no evidence that parents can do anything (such as avoiding peanuts during pregnancy and nursing) to prevent peanut allergy, according to Chad.

If you have a kid who’s allergic to peanuts, the most important thing you can do is educate yourself (and your child, when he’s old enough) about how to avoid foods that might contain peanuts, and how to use an EpiPen. And make sure this life-saving gadget goes everywhere with your child.

I can monitor my severely allergic child at home, but what about when he’s at school?

There’s been a growing awareness of the seriousness of severe allergies. For example, the Ontario government passed Sabrina’s Law in 2005, which makes it mandatory for the province’s publicly funded schools to have programs in place to protect kids at risk of anaphylaxis. It mandates that staff receive training in recognizing the symptoms and dealing with emergencies. In BC, the government recently passed similar regulations in the form of a Ministerial Order for school districts. (To find out what your home province is doing, visit allergysafecommunities.ca and click on Anaphylaxis Policies, then Policies in Canada.)

Yes. To start with, scientists are investigating promising treatments, including a peanut allergy vaccine. Preliminary studies also suggest it may be possible to prevent eczema by giving babies helpful bacteria called probiotics — the hope is that this might also halt the “allergic march” toward other allergy-related conditions like asthma and hay fever.

Researchers are also looking for other ways to prevent people from becoming allergic in the first place. The federal government has helped create a national centre for excellence in allergy research, bringing together top scientists to study why people develop allergies and how to intervene. “Allergies are on the map,” says Chad, “and the federal government has given a substantial amount of money for research into the causes of allergy. That’s a major good news story for Canada.”