The two terms tend to be used interchangeably, but knowing how they differ can help you manage your symptoms, prevent potential nutrient deficiencies, get the right treatment, and feel your best.

When your body misfires against seemingly innocent foods, could it be the start of a food allergy or an intolerance?

In a time when gluten-free options grace menus, schools are nut-free zones, and people boast about their dairy-free diets, we’re more aware than ever about food allergies and intolerances. But they are two very distinct conditions.

“A food allergy is an immune response where the body produces antibodies called IgE in response to a particular protein in the food,” explains Georgiana Sanders, MD, an associate professor at the University of Michigan Mary H. Weiser Food Allergy Center. The body attacks these typically harmless proteins, triggering an allergic reaction, which can appear within seconds or hours of exposure. To be diagnosed, you must exhibit symptoms such as hives; wheezing; runny nose; itchy eyes; or lip, throat, or tongue swelling; plus a positive blood test or skin prick showing the presence of antibodies. 

Fifteen million Americans have food allergies, and 9 million of those are adults. And it’s not your imagination: Allergies are on the rise in children and adults. Food allergies in kids spiked by 50% between 1997 and 2011, according to the Centers for Disease Control and Prevention. Preliminary research presented in 2017 at the American College of Allergy, Asthma, and Immunology found that 45% of adults with food allergies develop them in adulthood, most commonly to shellfish and tree nuts. There are two plausible theories to explain this increase in food allergies: the hygiene hypothesis (in essence, we live in a too-sterile environment), and the idea that delaying introducing certain foods to infants (particularly peanuts) may prevent budding immune systems from maturing properly.  

Want to learn more about food allergies? Read on: 

A food intolerance (also called a sensitivity) occurs when you have difficulty digesting a food, leading to gas, abdominal discomfort, or diarrhea, but there’s no immune reaction or antibodies produced. The most common intolerances are to lactose (a sugar found in milk), gluten (a protein found in wheat), and certain complex carbohydrates (from beans and cabbage). It’s best to talk to your doctor if you suspect a specific food is routinely causing digestive woes. Avoiding foods unnecessarily can lead to a nutrient shortfall in your diet, particularly if you remove multiple foods in a blind effort to heal symptoms. If you do have to steer clear of a type of food—for instance, dairy—a dietitian can help you plan your diet so that you’re getting other sources of calcium and vitamin D (like fortified nut milk).

What Kind of Tests Can I Take to Tell If I Have a Food Allergy or Intolerance?

Uncovering allergies and intolerances isn’t as cut-and-dried as it appears. Here are the tests to try and to skip when it comes to finding out what’s going on inside.

IgE antibody test 
The gold standard for allergy testing, but false positives are common. Or antibodies show up after you eat a food, but there are no symptoms (thus it’s not an allergy)—this could be the body reacting to factors like pollen.

Skin Testing
A common test that involves injecting the skin with a tiny bit of the allergen. Positive reactions will appear as a “wheal and flare” (a raised red area) that’s bigger than a control prick of saltwater.

At-Home Testing 
You can buy kits online that claim to provide insight on which foods trigger allergies or intolerances, but these tests have not been proven to be effective, says Sanders, and may lead you to eliminate foods unnecessarily.

Medical History
There are few tests to pinpoint specific intolerances (one such test is a hydrogen breath test for lactose intolerance); it’s more likely your doctor will make a diagnosis based on a medical history of your symptoms.

Food Elimination
If you suspect an intolerance, your doctor may suggest eliminating the suspected foods for six weeks. Add one food back per week, and record any symptoms you experience to reveal any telling patterns. 

Is Avoiding Food the Only Way?

You love lattes, but sometimes they give you tummy troubles. Other times eating in-season fruit makes your lips itch. Here’s what you need to do to stay symptom-free.

The only way to “treat” a food allergy is to avoid the offending food. But cross-contamination or unknowing consumption can make this hard. Each year, 200,000 people in the U.S. need emergency medical care for allergic reactions, according to Food Allergy Research & Education. As a result, most medical experts suggest that people with allergies carry epinephrine pens.

For intolerances, you may have more leeway when it comes to avoiding woes. If you’re lactose intolerant, you may be able to handle small amounts of milk or eat other dairy that contains less lactose, like hard cheeses and yogurt. A lactase tablet may also help.

If your mouth itches or your throat is scratchy after eating certain raw produce like apples, peaches, and zucchini, you may have what’s called oral allergy syndrome, a condition where your body has an allergic reaction to the pollens in foods. It can pop up in adulthood and typically occurs along with seasonal allergies. Your allergist may recommend taking an antihistamine, according to Mina Nguyen, MD, chief of the allergy departments for Kaiser Permanente in Oakland, California.