Allergy testing for toddlers

Sophie Vayro’s daughter Desa suffered from severe eczema as an infant; she also had reactions to some solid foods when they were first introduced. It concerned Vayro enough that she asked the doctor to refer them to an allergist for testing after Desa’s first birthday (the youngest age at which most doctors will do allergy testing).

Different tests, different results

The allergist did a skin-prick test, in which small amounts of the foods to be tested were injected just under Desa’s skin. A hive developed where Desa was tested with peanuts, indicating an allergy. Vayro was told to clear all nuts from her home and to carry multiple EpiPens whenever she went out with her daughter.

However, when Vayro later saw a naturopath, she was told that a blood test, which examines for specific proteins that are part of an allergic reaction, might give more information.

“On the blood test, peanuts showed up as only slightly reactive,” says Vayro. She waited until Desa was two, then asked to have another skin-prick test done. This time there was no reaction — no hive. “I was so relieved,” says Vayro. However, she was also a little confused about the varying results of the different tests.

Wade Watson, a paediatric allergy specialist in Halifax, says some of the confusion may arise from tests being done on a random assortment of potential allergens, which can give a false positive result. He explains that the most important part of diagnosing food allergies is getting a good history. “We need to know what symptoms the parents see and what the triggers seem to be,” he says. “Then you do testing based on that history to confirm the diagnosis.” In other words, you only test for foods when there is already some indication that the child might be sensitive.

Parents are usually right about kids’ allergies

Plus, Watson says, managing allergies is not a “one-visit type of thing.” Toddlers will often outgrow their allergies, and doing blood tests as a child gets older can confirm whether the level of reaction she has is low enough that a food challenge can be done. This is a two-hour process that involves the child eating increasing amounts — up to one serving — of the food in question, under observation in an allergist’s office or hospital.

This is the process Katriona Mitchell of Saskatoon is going through with her son James. Mitchell had a terrifying experience when she gave James barley cereal for the first time, when he was nine months old. He broke out in hives within three minutes, his face began to swell up, and he had trouble breathing. “I had to call 911,” she recalls. Sure enough, a month later, James had a strong reaction to barley in a skin-prick test.

It wasn’t until he was past his first birthday that Mitchell offered James a teething biscuit with wheat flour in it — and her son’s immediate reaction meant she had to head back to the hospital. “Once we realized he was allergic to wheat as well, we did skin-prick tests for all the grains, and he reacted to rye and oats too,” she says. Now four, James continues to go back for regular retesting to see if anything in his allergic status has changed.

While false positives are common, Watson says that negative skin-prick tests are a very good indicator that the child is not allergic to the food being tested. “However, the history is more important than the tests,” he reiterates. “I find that parents are right about the foods their children are allergic to 98 to 99 percent of the time.” The key, he emphasizes, is to keep track of toddlers’ food intake and reactions. “That’s what gives us the basis to do meaningful testing,” says Watson.

Keep it under observation

Rachael Ward of Waterloo, Ont., noticed her daughter had a rash on her chin for several months. “At first, I chalked it up to teething and chapped skin,” she says. “Then she had a very bad stomach flu and was off all solid foods and only nursing for about three days. The rash cleared up.”

Ward decided to reintroduce solid foods one at a time, to try to figure out what had caused the rash. “The day her grandfather was watching her, I suggested scrambled eggs for lunch as it was easy and one of her favourites,” recalls Ward. When she saw her daughter two hours later, the rash was back.

Based on these observations, Ward spoke to her doctor about a referral to an allergist, and he said, “You know she’s allergic. Don’t give her eggs.” In the end, Ward’s daughter was never tested. Today she’s seven, and tolerating eggs, although she has a mild reaction if she eats a lot of them. Ward finds that she doesn’t have to be as vigilant about foods in which eggs are one of many ingredients, but tends to stay away from foods that have a lot of eggs in them.

Delayed reaction?

Wade Watson, a paediatric allergy specialist in Halifax, points out that certain types of allergies cause children to react immediately, whereas others bring on less rapid reactions. Immediate-reaction symptoms typically occur within minutes of exposure (but can take up to two hours to appear) and involve more than one body system. Non-immediate-reaction symptoms occur three hours or more after exposure to the allergen, involve the intestinal tract only, and can be chronic. This type of symptom usually appears within the first year of a child’s life.

Immediate-reaction symptoms • hives • rashes • coughing • wheezing • swelling • tummy pain • vomiting

Non-immediate-reaction symptoms • severe vomiting • failure to thrive • blood and mucus in stools • diarrhea