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- Food allergies and food intolerances are not the same, but they’re sometimes confused for one another.
- A food intolerance is when someone has trouble digesting a certain food, leading to symptoms like gas or abdominal pain.
- A food allergy is when the body’s immune system overreacts to certain foods.
- Unlike an intolerance, a food allergy can cause serious or life-threatening reactions, even if the allergic person eats a microscopic amount of the food, touches it, or inhales it.
Food intolerances are not the same as food allergies, but it seems a lot of people mistake one for the other.
A study published January 4 in the journal JAMA Network Open found that about half of US adults who think they have a food allergy actually don’t. Instead, the authors said, those people who think they’re allergic might be experiencing symptoms of food intolerance, a reaction that may produce similar symptoms but is less dangerous.
Here’s a simple breakdown of the differences between the two.
Intolerance is when someone has trouble digesting a food
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Food intolerance involves the digestive system. It occurs when someone has trouble digesting a certain food, leading to symptoms like gas, abdominal pain, and diarrhea, according to the American Academy of Allergy Asthma & Immunology (AAAAI).
“In [food intolerance] situations, it is not a life-threatening allergy … but it does impair quality of life,” Dr. Michelle Hernandez, associate professor of pediatrics at the University of North Carolina at Chapel Hill, said in a video explainer published by the AAAAI in 2018.
Food intolerance can have different causes, allergy specialist Dr. James T C Li wrote in a 2017 post for the Mayo Clinic last year. In some people, it may be caused by the chronic condition irritable bowel syndrome. Others may be sensitive to food additives like sulfites, which are used to preserve dried fruit and wine. It can also happen when someone lacks an enzyme needed to break down certain foods.
For example, people who are lactose intolerant are deficient in the enzyme lactase, which the body needs to break down lactose, a natural sugar present in cow’s milk.
Finally, those with food intolerances may be able to eat small amounts of their trigger foods without experiencing any major issues, according to the AAAAI.
In food allergies, the body’s immune system overreacts to a food
A food allergy, by contrast, involves the body’s immune system.
When someone eats a food to which they’re allergic, their immune system overreacts to a specific protein in that food, the AAAAI explains. Eggs, fish, shellfish, peanuts, tree nuts, wheat, soy, and cow’s milk account for the majority of allergic reactions.
These reactions normally occur just minutes after exposure to the food, and the symptoms can include hives, itchiness, swelling in the skin, stomach cramps, vomiting, diarrhea, and respiratory problems like sneezing or a stuffy nose.
In some cases, food allergies cause anaphylaxis, a severe reaction signaled by tightness in the throat or chest, wheezing, trouble breathing, and tingling in the hands, feet, lips, or scalp. If not treated immediately with an injection of epinephrine, it can be fatal.
Intolerances and allergies can share some gastrointestinal symptoms. But unlike intolerances, food allergies can be life-threatening, even if the allergic person consumes a microscopic amount of the food, touches it, or even breathes it in. Some food allergens can travel through the air and cause reactions when inhaled.
See an allergist if you think you have a food allergy
The AAAAI recommends seeing an allergist if you think you may have a food allergy or if you’re avoiding certain foods because you think you’re allergic to them. Doctors can diagnose food allergies by analyzing your medical history and employing certain tests, like a skin prick test, a blood test, or a food challenge, in which a food is consumed in a medical setting to see if it prompts a reaction.
If you think you might have a food intolerance, your best bet is to ask a doctor or dietitian for help, rather than seeking out unproven tests that claim to detect food intolerance.
Some commonly available tests promise to diagnose multiple food sensitivities by measuring Immunoglobulin G (IgG) antibodies, but many expert organizations (including the AAAAI) recommend against using them, saying they lack solid scientific backing.
“It is important to understand that this test has never been scientifically proven to be able to accomplish what it reports to do,” the AAAAI website said in a post about IgG testing.
In an October 2018 article for SELF, registered dietitian Tamara Duker Freuman also warned against IgG tests. Instead, she recommended keeping a detailed two-week diary of what you eat and any symptoms you experience.
“Bring this information to a reputable registered dietitian – ideally one who specializes in food allergy or gastrointestinal issues and doesn’t sell any supplements – so that they can help you identify the common threads among likely trigger foods or meals,” she wrote. “This exercise will most likely yield a sane, manageable diet trial that you can undertake toward identifying the precise nature of your symptoms.”
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