Food Allergy vs. Food Intolerance: What is the difference?

What is the difference with an allergy and a food sensitivity?

What happens when your food is not compatible with your body? Do you experience gastrointestinal issues or bloating and fatigue when you eat? Or maybe you suddenly get an onset of skin rash or a migraine when you eat your beloved takeout? Don't worry; you are not alone. 

26 million

Suffer from a food allergy.

65 million

Suffer from a food intolerance.

Statistics show that up to 26 million Americans may suffer from a food allergy, and over 65 million may suffer from food intolerance. However, these statistics may be on the low side because some people are not properly diagnosed. 

Statistics show that up to 26 million Americans may suffer from a food allergy, and over 65 million may suffer from food intolerance. However, these statistics may be on the low side because some people are not properly diagnosed. 

The symptoms of a true food allergy are different from those caused by an intolerance. Allergies can be severe and life-threatening, involving the immune system. Food intolerances are generally milder and do not involve the immune system. Food intolerances usually involve the cells, digestive system, or a deficiency in a particular enzyme, which means that particular food isn't being broken down and digested properly by the body. 


What is a food allergy?

A food allergy can cause severe symptoms or even a response known as anaphylaxis in some people. Allergic reactions can occur even from the smallest amount of the offending food item, triggering a range of immediate responses. Food allergy reactions can take seconds to minutes to show signs and symptoms. 

Milder allergic reactions to a trigger can be: 

  • Coughing

  • Wheezing 

  • Itching

  • Runny or stuffy nose

  • Watery red or puffy eyes

More severe allergic reactions to a trigger can be: 

  • Tingling in the mouth

  • Swelling of the lips, tongue, face, or throat

  • Hives

  • Anaphylaxis

Anaphylaxis symptoms:

  • Constriction and tightening of the airways

  • Shock with a severe drop in blood pressure 

  • Dizziness or lightheadedness and sometimes a loss of consciousness

  • Fast racing heartbeat or pulse

It is very important to rule out allergies first by consulting your medical professional.

Why do allergies develop? 

Food allergies can develop at any time. However, they are more common in young children and usually can be lifelong. Scientists do not yet fully understand why or how someone develops allergies. The most common foods which may cause allergies: 






Shellfish or Fish

Tree Nuts

When to see a doctor

See your allergy specialist or doctor if you notice symptoms resembling a food allergy. However, you must seek urgent emergency treatment if you start to develop signs or symptoms of anaphylaxis.  

How is an allergy tested?

Allergies are usually identified via a blood sample, skin prick, or scratch test. A blood sample is required to identify the immune system's response to the suspected trigger. The allergy test will determine the reaction of your immunoglobulins (IgG, IgE, IgM, IgA) located inside the blood when that particular trigger item is mixed. Doctors may also use blood tests to help identify immunodeficiencies (i.e., when the immune system isn't working as it should).

How do I know if I have a food intolerance or sensitivity?

Intolerances or sensitivities can have a delayed response time and usually involve the digestive system or the cellular reaction to a particular trigger. Reactions can take between hours or days to show signs. The delayed onset of responses from a food intolerance may mean that food intolerances may be harder to identify due to the many different single items a person may have been exposed to or consumed within that period. 

Food Intolerances

What are the symptoms of food intolerances?

Food Intolerance symptoms may range from:

  •  Digestive issues, such as constipation, bloating, flatulence, gas, and diarrhea

  • Excess mucus in the throat or nose

  • Skin conditions, such as acne, rosacea, psoriasis, and eczema

  • Weight gain, or water retention

  • Decrease energy and lethargy 

How is a food intolerance tested?

Food intolerances may be tested in various ways:

Hydrogen breath test

The hydrogen breath test is a medical test measuring hydrogen gas levels (H02) in a person's breath. When the body is not breaking down sugars from lactose (milk protein), glucose (sugars from carbohydrates), or fructose (sugar's from fruits), it is then fermented by bacteria in the small intestine and the colon.

The hydrogen is absorbed from the intestines, carried through the bloodstream to the lungs, and exhaled. This is an excellent option for people wanting to target dairy intolerances, gluten intolerances, and fruit intolerances.

Food Diary / Self-Elimination Diet 

An elimination diet involves noting down all the food and drinks consumed daily and monitoring any reactions that may take place over a few hours to a few days. To start a food diary, you can buy a food diary online or use food diary apps to track every item. 

Food Sensitivity or Intolerance Test

At-home food sensitivity testing kits require a person to submit a sample, which could be:

  • blood from a skin prick test

  • strands of hair

  • a mouth swab

It may take up to several weeks to receive the results.  

Why do food intolerances develop? 

The most common reason food intolerances develop is the absence of a particular enzyme, which can cause improper digestion and uncomfortable symptoms. Every food item which is consumed requires a certain enzymatic process to break down that food fully and then absorb the nutrients from that food. For example, where there is a lactase deficiency, the lactose found in milk cannot be broken down. The sugar found in lactose remains undigested and intact, causing the bowels to ferment the sugar found in lactose resulting in bloating and gas. This is often referred to as lactose intolerance.

Lactose intolerance has been found to be very common in North America. Research has found that through evolution, the population is genetically programmed to lose their lactase enzymatic ability after a certain childhood age. There is still hope! Depending on the level of symptoms, you may still be able to ingest lactose-based foods (such as milk and cream) if a lactase digestive enzyme is consumed with every lactose-based meal to help break down the lactose. 

Other conditions of a food sensitivity or a food intolerance:

Caffeine Sensitivity

When people produce less of a liver enzyme called CYP1A2. This plays a role in how quickly the liver metabolizes caffeine.

Sulfite Sensitivity

This is when people may have a partial deficiency of the enzyme sulfite oxidase, which helps break down sulfites in food items such as dried apricots, canned fruits, wine, and cereals.


When a group of sugars ferment in the digestive tract due to an imbalance in bacteria. Enzymes such as amylase and glucoamylase, cellulase, lactase and invertase, and other enzymes break down FODMAPs. FODMAP foods include beans and lentils, some vegetables such as onions, garlic, and cauliflower, some fruits such as apples, cherries, and mango.

Sucrose Intolerance

Sucrose intolerance or genetic sucrase-isomaltase deficiency (GSID) is the condition in which sucrase-isomaltase, an enzyme needed for proper metabolism of sucrose (sugar) and starch (e.g., grains), is not produced or the enzyme produced is either partially functional or non-functional in the small intestine. Sucrose is found in sugar, sugary drinks, fast food, and baked goods.

Sugar Alcohol Sensitivity

(sorbitol, mannitol, maltitol, lactitol, isomalt) - this is when a series of sugar alcohol enzymes are deficient in the body, causing bloating and gastrointestinal distress. Sugar alcohols are found in most jellies, candies, ice creams, chocolate, chewing gums, protein powders, prunes, and berries.

Fructose Intolerance

Alterations in the ALDOB gene can cause hereditary fructose intolerance. The ALDOB gene provides instructions for making the aldolase B enzyme. This enzyme is found primarily in the liver and is involved in fructose breakdown (metabolism), so this sugar can be used as energy. Fructose is found in most fruits.

The Takeaway

There are significant differences between food allergies and intolerances to be aware of. Food allergies affect the immune system, and food intolerances involve the cells and the digestive system. While food intolerances may not be life-threatening, food allergies can be, and this is why it is essential to rule out allergies.

It may also be possible that you may not be allergic to a certain food item but intolerant, and vice versa. This is because the immune system can react differently to the digestive system and cells of the body.

Food allergies can happen quickly and can be triggered even by the smallest portion of food. In contrast, food intolerances may require more significant amounts of that food intolerance trigger and can take between hours and days to show signs or symptoms.

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