Bans on foods, especially nuts, have become common on schools, and across entire school boards, in recent years. One consequence: the near-disappearance of the lunch box peanut-butter sandwich that the parents of today’s children remember. But it’s not hard to find experts in children’s allergies who say they’re not warranted.
Food allergies are overdiagnosed for several reasons, Chan explains.
The initial tests for allergies – skin tests and blood tests – often have false positive results. A ‘challenge test,’ which involves slowly increasing exposure to the suspected allergen under medical supervision, is more accurate.
The result is that more parents are told their child has a food allergy than actually do.
“When we look at skin tests and specific IGE blood tests, which are the two most readily available tests for food allergies, many aren’t aware that a negative result is fairly reliable, but a positive result can be quite inaccurate. A positive result can occur in a child who tolerates the food and has no true food allergy, yet the skin test or blood test is positive. It’s an actual flaw in the test.”
“Many children that get referred to allergy clinics, when they have had positive tests, either skin testing or IGE blood testing, often don’t have true food allergy.”
This is why doctors discourage parents from having children who haven’t shown any sign of an allergy tested pre-emptively, Chan explains.
“We do not advise that infants get routine testing to a food prior to ingestion, because of the potential for there to be clinically false positive results and generation of confusion.”
“If the child who tolerates eating the food wasn’t tested in the first place, the parent wouldn’t be grappling with whether or not the child is allergic to food. The decision to test should entirely be based on the history.”
Some food allergies are more dangerous than others, but Chan says it’s very difficult to predict which is which.
“There isn’t a simple test to do that. The severity is based more on co-factors, such as whether the patient has asthma, whether the patient had an illness on the day that they accidentally ate the food, whether the patient ate the food in a greater food mixture, the quantity of the food, whether the patient has had severe anaphylaxis to the food in the past, the type of the food – it’s a real collection of factors that impact on severity.”
Food bans in our schools – Read the entire 5-part series here:
- Part 1: Why many medical experts think food bans in schools go too far
- Part 2: Why are food allergies linked to income?
- Part 3: Allergy tests full of false positives, doctor explains
- Part 4: Nut-free peanut butter substitutes are often banned
- Part 5: Is desensitization therapy for allergic kids a way out?
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