What’s The Threshold For Food Allergies?

Those with food allergies have no choice but to become food vigilantes, combing food labels for the ingredient list or information like “may contain nuts” to see if they can eat it. 

In some folks, even the tiniest traces of allergen can trigger a reaction. The sensitivities of those with peanut allergies has been widely written about, and other foods can be just a tricky: In one case, a young woman who is allergic to shellfish ended up in the emergency room after an innocent goodnight kiss from her boyfriend, who had just eaten shrimp.

If you or a loved one has a food allergy this severe, the above chart is not for you.

Many others with food allergies can tolerate up to certain amount of their allergen before symptoms set in. But how many grams of the offending allergen are enough to set off an allergic reaction? Researchers now have an answer, presented in the infographic above. The new study, from the University of Manchester, has unearthed the very low levels at which five of the most common food allergens would cause a reaction in the 10 percent of those most sensitive to them.

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Food allergies are now estimated to affect up to 5 to 7 percent of infants and 1 to 2 percent of adults. Those that hit in infancy are dominated by cow’s milk and hen’s eggs but are largely outgrown by school age. However, allergy to peanut persists into adulthood, and is the dominant allergy in the United Kingdom, France, North America, and Australia.

Food allergies can also change with age, with adults being more likely to develop allergies to shellfish, seafood and fresh plant foods.

With the number of people being diagnosed with food allergies rising significantly in the past few decades, the study, done by researchers at the University of Manchester is “part of the background to rolling out new warning guidelines across Europe” in regards to food safety and public health in regards to those with allergies, says Professor Clare Mills, one of the lead researchers for the study.  This new research will help determine the smallest amounts of an allergen that could prove to have a serious risk for effected individuals.

"An example of this might be a chocolate bar that carries a precautionary statement ‘may contain hazelnut’," Mills tells Yahoo Health. "Should a hazelnut allergic individual avoid this product? If an action level was identified for hazelnut it might be that an allergic individual who only reacted if they consumed a gramme of hazelnut protein could safely eat the chocolate bar.  If an action level was set for less than of 1.5mg hazelnut protein per food serving this would allow at least 95% of the hazelnut allergic population to be protected."

Related: Why You Need To Stop Lying About Having Food Allergies 

"The data from the study also shows that individuals with allergy to shrimp had to eat several grams of well cooked shrimp flesh to have an allergic reaction," adds Mills. "This means that traces of shrimp in processed foods are unlikely to pose a risk of reaction in the majority of shrimp allergic individuals."

The brave study participants had one of the five most popular food allergies — hazelnut, celeriac, peanuts, fish and shrimp — or had shown a sensitivity to one of the foods on a skin scratch test. They consumed doses of foods either alone or containing the allergen until they had an observable reaction or reported persistent and/or severe subjective reactions.  They received increasing doses of the allergen at intervals of 20 minutes starting with 3 mg of protein up to a cumulative dose of 1 to 6 grams of protein depending on the food. Reactions had to occur 2 or less hours after the last dose.

This new information will re-contextualize how we approach allergen warnings on food packaging (aka those pesky notes in the fine print on consumer packaged goods that warn that a product is produced in a factory also containing peanuts, wheat, eggs, etc), helping European officials redefine the lowest levels of an allergen needed for food labeling purposes, hopefully making for a safer, healthier eating.