Are food allergies really on the rise?

Joanne Harris grew up in a dairy family. Her grandfather owned the farm and her father worked it with him. “Milk went into everything Mom baked and made,” says Harris, remembering her childhood in the 1960s and 1970s in Nova Scotia’s Annapolis Valley. “We used to drink milk right from the cow.”

Researchers looking into the causes of food allergies might have considered Joanne the poster child for what they call “the farming effect,” a set of environmental conditions that protects against the development of allergies. The evidence uncovered by Swiss researchers in the 1990s narrowed the key ingredients that prevented the vast majority of farm kids from developing allergies to three: livestock such as cows, the type of fodder fed to livestock and the drinking of raw milk—all things that Harris would have been exposed to on a daily basis pretty well from birth.

As researchers would expect of a farm girl, Harris could eat almost anything she liked, until recently. At the age of 46, something suddenly changed. Joanne started suffering from stomach cramps, nausea and diarrhea. “It turned into a full-blown sickness,” says Harris. “I had allergy testing and found out it was milk.” Tests also revealed that she was sensitive to certain seafoods and food dyes.

People around Harris’s age or older didn’t know what a peanut allergy was when they were kids and had never heard of gluten. But in the past couple of decades, many elementary schools have banned peanuts altogether and gluten-free foods are common. But are food allergies really on the rise or are we just more aware? If they are, what’s behind this increase and what can we do to mitigate their effects once they occur?

Food allergies explained
At birth, the immune system begins to develop as the body learns which microbes are harmful and which are not. When the immune system encounters a harmful microbe, it creates immunity to it by building antibodies. But in some children, something goes wrong with the identification process and the immune system creates antibodies to harmless proteins in things like peanuts, wheat or milk. The next time the system is exposed to that protein, the antibody binds with it and gives off chemicals such as histamine, which can cause mild to severe to life-threatening reactions in the respiratory system, gastrointestinal tract, skin or cardiovascular system. This is why swelling in the airway, hives and nausea are the symptoms of an allergic episode.

The most recent statistics from Health Canada put the number of young children who have physician-diagnosed food allergies at five to six per cent. For adults, it’s three to four per cent. The agency has identified a top-10 priority list of food allergens: eggs, milk, mustard (a recent addition), peanuts, seafood (including fish, crustaceans and shellfish), sulphites (found in many processed foods), sesame, soy, tree nuts, and wheat and other grains containing gluten.

“World experts have said there was a trend. If you look at 40 or 50 years ago versus now, there probably are some differences,” says Dr. Wade Watson.

Dr. Watson is a pediatric allergist, head of the Division of Allergy at the IWK Health Centre in Halifax and a professor of pediatrics at Dalhousie University. He’s quick to downplay the cries of an epidemic. “Since the early 90s there has been no significant difference. I think there’s more interest and people are more aware. In the last five or 10 years, it’s still about six per cent of children.”

He adds that increases in true allergies among adults are even less likely. For one thing, it’s rare for adults to develop a true allergy in the first place. “In the last 28 years, the number of new food allergies I’ve seen outside of childhood is very, very low.”

Still, Dr. Watson admits that changes in lifestyle may account for a small increase over several decades. “There are theories—changes in the way we feed our children, changes in diet, the number of children in families, our bodies’ immune system reacting differently. It might have to do with more frequent use of antibiotics. There’s one theory that a lot of people dispute called the hygiene hypothesis.”

Dr. Watson calls on his own childhood as an example of how this hypothesis works. “When I was small, I was ninth of 10 children and lived in rural Nova Scotia. You were sent out to play. You went to the garden. If you wanted a carrot, you pulled it out, brushed the mud off on your leg and ate it.” As with Harris on the family dairy farm, Dr. Watson was exposed to those microbes—both in the garden and from his siblings—that at an early age encourage the development of a robust immune system.

These are all intriguing and promising theories, according to Dr. Watson, but he says, “None adequately explains it.” Theories about causes and increases don’t much concern him anyway. “It really is irrelevant because what we have is what we have. There’s no intervention I can think of that’s going to decrease the chances of developing allergies.”

Dealing with your allergies
While the doctor who diagnosed Joanne Harris’s food allergies has never named a cause, Harris thinks she knows. “In the winter of 2013, I had my gall bladder removed. From then on, I wasn’t feeling well. They say the anesthetic will sometimes bring on allergies.” Some medications like anesthetics and antibiotics may affect the gut flora and cause sensitivities and perhaps even food allergies.

When it comes to the identification of food allergies in such cases, Dr. Watson says, “There are certainly a lot of people who feel they have problems with milk and gluten, but an intolerance is very different than an allergy.”

Allergies, he says, involve the immune system, while a food intolerance is mostly about the breaking down or absorbing of food. “Food intolerances just make you uncomfortable, but they are not going to kill you. A food allergy can kill within minutes.”

Dr. Watson notes there is promising new research in the treatment of food allergies like slowly increasing the exposure to an allergen like peanut protein, but so far these have only been carried out under research conditions. “It’s not a cure,” says Dr. Watson. Rather, a good strategy is to avoid the food you’re allergic to and wait it out. “Many children who are milk, egg, and wheat-allergic early in life will have outgrown that allergy by age five.”

Adults like Harris who develop reactions to foods—whether by allergies or intolerances—simply have to live with changes in lifestyle. “We enjoyed eating out at restaurants, but that has changed,” says Harris. “You can’t just go and have a meal.” Still, she says, it’s not all bad. “It’s turned into quite a healthy diet. I drink a lot of almond milk, fruit smoothies, lots of fresh fruits and vegetables.”