What are food allergies and what should you look out for?

Food allergies happen when your body’s immune system mistakes harmless food proteins as dangerous. This can lead to a wide range of symptoms, including rashes, breathing difficulties, and diarrhea.

In rare cases, a severe allergic reaction to food can lead to anaphylaxis, which can be fatal if not treated immediately.

Food intolerances are often mistaken for food allergies, but intolerances mostly trigger digestive issues and do not cause anaphylaxis.

If you have a reaction to eating a certain type of food, see a healthcare professional to find out whether you have an allergy or an intolerance.

It is not clear why some people develop food allergies and others don’t. Scientists believe that a combination of a person’s genes and their environment contribute to their risk of food allergies.

A relatively new area of research is the gut microbiome and food allergies. The gut microbiome encompasses trillions of bacteria and other microbes that live in your intestine. 

Some studies suggest that changes in the gut microbiome occur before someone develops a food allergy, pointing to a link between the microbial inhabitants of your gut and your risk of food allergies. 

Below, we’ll review in more detail the causes and symptoms of food allergies, the most common food allergies, and the key differences between food allergies and food intolerances.

What are food allergies?

Food allergies occur when your immune system mistakes harmless food proteins as dangerous invaders and reacts to them with an immune response. 

Even though these food proteins are harmless for the rest of the population, for people with food allergies, they can be harmful or even life-threatening. 

Around 1 in 13 children and 1 in 10 adults in the United States have a food allergy, and this rate is on the rise. It’s possible to develop a new food allergy at any point during a person’s lifetime, not just during childhood. 

Nearly 1 in 5 adults believe they have a food allergy. There is much that scientists still don’t fully understand about food allergies, and diagnostic tests don’t always capture the more complex types of food allergy

That’s why it’s important to work with a healthcare professional to get a diagnosis if you have any reactions to food.

There is no cure for food allergies, but there are treatments that can help people manage their symptoms. 

Symptoms of food allergy

Food allergies can affect numerous parts of the body and may cause a range of symptoms from mild to severe:

  • hives

  • itchy red rashes

  • swollen lips or face

  • swollen throat and difficulty swallowing

  • wheezing or difficulty breathing 

  • feeling dizzy or lightheaded

  • feeling sick or vomiting

  • stomach pain or diarrhea

  • sneezing

  • itchy eyes

  • anaphylaxis

These symptoms can appear very rapidly or much later on, depending on the allergy.  

A severe food allergy can be life-threatening and can lead to anaphylaxis, sometimes known as anaphylactic shock

Anaphylaxis can include many of the symptoms listed above, as well as an increased heart rate, abnormally low blood pressure, and a sense of impending doom that something bad is about to happen.

If untreated, anaphylactic shock can damage your internal organs or lead to a heart attack. If you have a food allergy and are at risk of anaphylaxis, your doctor may give you an epinephrine pen to carry with you. 

Epi-pens deliver a dose of epinephrine. Epinephrine is a hormone, also known as adrenaline.

When injected in an emergency situation, an epi-pen relieves the life-threatening allergic reaction by increasing blood pressure, stimulating your heart, and boosting blood sugar

The most common food allergies

According to the U.S. Food and Drug Adminstration (FDA), there are eight allergens that account for 90% of food allergies in the U.S.

The eight most common food allergies are:

  • milk

  • tree nuts, like hazelnuts 

  • eggs

  • peanuts

  • fish

  • wheat

  • shellfish

  • soybeans

Packaged foods that contain any of these allergens are required by law to carry a label that points out the allergen source. 

The FDA recognized sesame as the ninth major allergen in 2021. From 2023 onward, foods containing sesame have to classify it as an allergen source on the food label.

Food intolerances

Food intolerances do not involve the immune system. Rather, they are reactions to certain foods or molecules within foods. Scientists estimate that food intolerances affect up to 20% of the population. 

In most cases, symptoms of food intolerances manifest in the form of digestive issues such as cramps, constipation, bloating, and diarrhea

Food intolerances are multifaceted and do not always have a clear cause. Work with a healthcare professional to establish the cause of your symptoms before restricting your food intake. 

Examples of food intolerances include:

  • A lack of a specific enzyme to properly digest a type of food. People with a lactose intolerance do not have adequate amounts of the enzyme lactase in their small intestine. They can't digest lactose properly in their gastrointestinal tract, which causes bloating, gas, and changes in bowel movements.

  • Digestive reactions to high-FODMAP foods can cause food intolerance symptoms in individuals with irritable bowel syndrome (IBS). FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.

Celiac disease is neither an allergy nor a food intolerance. It is a serious autoimmune system condition in response to eating gluten.

People who have celiac disease experience severe reactions to gluten-containing products and must take lifelong precautions to avoid them.

If you have a reaction after eating a particular food, it’s important to discuss your symptoms with a healthcare professional who can advise on the best options for managing a food intolerance. 

They may recommend reducing or cutting out specific foods from your diet. 

The gut microbiome and food allergies

In recent years, researchers have found links between the gut microbiome and food allergies. Your gut microbiome is the biological community of trillions of bacteria and other microbes that live in your gut. 

The health of your microbiome impacts your overall health, and some scientists have started referring to the microbiome as an organ itself. 

There's evidence that microbiome imbalances may precede food allergies. Some studies have found differences in the composition of the gut microbiome between people with food allergies and those without them. 

At ZOE, we don’t test for allergic reactions or food intolerances. If you believe you may have a food intolerance or allergy, you should consult your doctor. 

Our scientists run the largest collection of studies of nutrition and the gut microbiome in the world.

From our research, we know that your gut health and your overall health are linked to the makeup of your gut microbiome and that everyone’s gut microbiome is unique. 

ZOE scientists have identified 15 “good” bugs that are linked to better markers of health and 15 “bad” gut bugs that are linked to markers of worse health. By taking the ZOE test, you can find out which of these bugs live in your gut. 

The ZOE program also tells you which foods make up your personal “gut boosters” and “gut suppressors.” 


Whether or not you develop food allergies depends on many factors including your genes, your environment, and possibly your microbiome

Food intolerances predominantly affect your digestion, and food allergies are an immune response. 

Nearly twice as many people believe they have a food allergy than laboratory tests confirm. However, there are some food allergies that scientists have not developed specific tests for yet. 

Talk to your doctor if you have any reactions after eating, to ensure you receive a full assessment and diagnosis.  

There is no need to cut out any food unless advised by a healthcare professional.

At ZOE, we don’t test for food allergies or intolerances. But we can help you understand more about your unique microbiome.

We know that there is no “one-size-fits-all” answer to nutrition, and our personalized program can help you find the best foods for your metabolism and your gut microbiome. 

Take a quiz to find out how ZOE can help you learn more about your unique microbiome.


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