Food Allergy vs. Food Intolerance: Signs, Symptoms, and Differences
Health Conditions

Food Allergy vs. Food Intolerance: Signs, Symptoms, and Differences

Food Allergy vs. Food Intolerance: Signs, Symptoms, and Differences

Posted 2 months ago

SaVanna Shoemaker, MS, RDN, LD

SaVanna Shoemaker, MS, RDN, LD


We all love food, but sometimes food doesn’t love us back. Food allergies, food intolerances, and food sensitivities are thought to affect anywhere from 20-40% of the population.[*][*]

If you haven’t been introduced to this world as a result of your own adverse food reactions (or those of a close family member or friend), then you may be unclear on the difference between food allergies, food intolerances, and food sensitivities. 

The biggest difference between these issues is their root cause; otherwise they can be pretty similar. Foods that people are commonly allergic to are also foods that people are regularly intolerant of, and the symptoms can be similar too. Even health professionals can sometimes struggle to differentiate between food allergies and food intolerances.

However, if you suspect you may have one, it’s important to understand their differences so that you are fully equipped to take care of your health. 

In this post, we’ll review food allergies, food intolerances, how they're similar and different, and what we can do about them.

What Is a Food Allergy?

A food allergy, simply put, is when the body has an immune response to a certain food. For more information, check out our post on managing food allergies.

The symptoms can range from mild, like hives or itching, to severe and life-threatening, like anaphylaxis. 

Anaphylaxis is a severe allergy complication characterized by swelling of the face, mouth, and throat — which can inhibit breathing and may even be fatal.

For this reason, food allergies are a serious condition and should be handled extremely carefully. People with food allergies must be vigilant about the food they consume because one accidental ingestion of an allergen can have serious health consequences. 

Most people with food allergies carry epinephrine injections with them at all times. These injections can be used to reduce airway swelling if they enter anaphylactic shock after allergen exposure. 

Common Food Allergens

People can be allergic to anything, but the most common food allergens are typically referred to as the “Big 8.” These are:

  • Milk
  • Eggs
  • Fish
  • Shellfish
  • Tree nuts
  • Peanuts
  • Wheat
  • Soybeans

As of 2023, the United States will officially be adding sesame to its list of major allergenic foods.[*]

How to Identify a Food Allergy

Food allergy reactions are often immediate and happen within minutes to hours after ingesting an allergen.

However, the only way to confirm you are allergic to a food is via allergy testing with a healthcare provider. This testing often involves pricking the skin with minimal amounts of the most common allergens and monitoring the reaction at each skin prick site.

What Is a Food Intolerance?

Food intolerances differ from food allergies because the body’s reaction occurs within the digestive system. It’s not an immune response. Instead, food intolerances generally happen because the body lacks an enzyme needed to fully digest a certain food component. 

Additionally, unlike food allergies, the body’s immediate response to a food intolerance tends to be less severe.

Generally, the symptoms of a food intolerance occur shortly after eating a trigger food and are digestive in nature — like gas, bloating, and diarrhea.

Food intolerances can be clues that your gut health may not be optimal, and poor gut health could lead to further health complications down the road. 

The most common food intolerance is lactose intolerance, caused by insufficient levels of lactase — the enzyme that breaks down lactose, a type of sugar found in milk.[*]

However, food intolerance is not always a black-and-white issue. For example, Celiac disease is an immune response to gluten (found in wheat, rye, triticale and barley). It is NOT an allergy, but can have more severe health implications than a non immune-mediated food intolerance. 

Food Intolerance vs. Food Sensitivity

Although many people use the terms “food intolerance” and “food sensitivity” interchangeably, there are some minor differences between the two. Food sensitivities are often defined as symptoms that aren’t related to a food intolerance, an allergy, or Celiac disease. These are thought to be potentially some type of non-allergic immune reaction, but research is ongoing.[*]

The most common food sensitivity appears to be non-Celiac gluten sensitivity.[*]

Common Food Intolerances

Here are the most common food intolerances[*]:

  • Dairy products: due to lactose (a sugar) or casein (a protein)
  • Eggs: typically a sensitivity to a protein found in egg whites
  • Monosodium glutamate (MSG) and other food additives: found in many processed foods
  • Histamine: found in alcohol, fermented foods, dried fruits, processed meats, aged cheeses

How to Identify a Food Intolerance

Many people identify their food intolerances by accident. Over time, they may realize that every time they eat a certain food, they experience some unpleasant symptoms.

Others start an elimination diet to help pinpoint foods that may be problematic for them. 

There are also several different medical tests available to help detect and differentiate between various food intolerances.

If you are having unexplained digestive symptoms (or any symptoms at all, really), it’s a great idea to start keeping a food journal with notes about your symptoms, their time of onset, and what you ate prior to experiencing these symptoms. 

The Key Differences Between Allergies and Intolerances

Allergies and intolerances are often confused because they share symptoms, and many common allergens are also foods that people are commonly intolerant to. Here are some of the key differences between the two:

  • Causes. Allergies and intolerances have different causes. While food allergies are immune-driven, food intolerances are typically caused by a deficiency of a particular digestive enzyme. For instance, lactose intolerance is also commonly known as lactase deficiency.
  • Levels of severity. Allergic reactions can range in severity from mild to deadly and happen in minutes to hours after allergen exposure. While intolerance reactions also occur shortly after consumption, they tend to be less severe — although they can still be very uncomfortable and may lead to other complications.
  • Symptoms. Food intolerance reactions tend to be more gut-focused: bloating, diarrhea, nausea, abdominal pain, gas, etc. Allergic reactions can present with these symptoms but may also cause hives, itching, and anaphylaxis.
  • Management and treatment. Allergy treatment involves strict avoidance of the allergen and emergency management of symptoms in case you are exposed. However, people with food intolerances may have other options besides strict avoidance, such as including specific digestive enzymes in their diet.

Can Allergies or Intolerances Be Overcome?

Some evidence suggests that allergies may be prevented with early childhood exposure to common allergens. For instance, exposure to peanuts in infancy is a common practice to help prevent peanut allergies.[*]

Fortunately, many babies and young children also grow out of allergies to milk and soy as they get older.

However, allergies aren’t curable. The best way to avoid an allergic reaction is to strictly avoid the allergen itself.

On the other hand, there are more options for food intolerance. Of course, avoiding the food you’re intolerant to is the most reliable option. However, digestive enzymes may also help. For instance, people with lactose intolerance can take over-the-counter lactase supplements to reduce their symptoms when eating dairy foods.

Additionally, although some food intolerances may not be completely reversible, there is some evidence to suggest that probiotics and prebiotics may help to improve lactose intolerance by supporting gut health.[*]

Either way, you may benefit from working with a functional medicine practitioner to optimize your gut and immune health. 

What To Do If You Suspect a Food Allergy or Intolerance

If you suspect a food allergy or food intolerance, make an appointment with your healthcare provider.

While waiting for your appointment, keep notes about what you eat, when, and any symptoms you experience. This can help your healthcare team pinpoint potential causes and order the proper tests.

However, be sure to seek emergency attention if you have a serious reaction to food.

While food allergies and food intolerances can be really limiting and stressful, dealing with them must become a daily reality if you are diagnosed. Knowledge and the right tools are key for staying safe and managing your condition well.

Carb Manager allows you to filter recipes and foods by allergens as well as other common food sensitivities and offers support for common food intolerance elimination diets — including low FODMAP, Whole30, and Autoimmune Protocol. The notes feature is also a helpful way to track your symptoms when you’re in the midst of an elimination diet or if you suspect a food intolerance or sensitivity. 

Be sure to seek professional help too, especially if you think you may have a food allergy.