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Signs of Food Allergy vs. Food Intolerance
Updated on January 31, 2024
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Diet / Weight Loss
Signs of Food Allergy vs. Food Intolerance

We often confuse a food allergy with food intolerance. It may be because these two have very similar symptoms.

However, they are not the same. One is more life-threatening than the other. Most people who react to certain foods have food intolerances, not food allergies.

Our resident medical reviewer, Dr. Rizza Mira, will help us shed light on the key differences between food intolerances and food allergies.

Dr. Mira is an expert in diet and nutrition, and has clinical experience in public health.

Signs of Food Allergy vs. Food Intolerance 2

What is a Food Allergy?

A food allergy is your immune system’s reaction to certain foods. Even a tiny amount of food can trigger this reaction.1

The adverse reaction happens whenever you consume foods you’re allergic to. So it’s best to avoid them altogether.

What Causes Food Allergies?

A food allergy occurs when your body’s immune system falsely identifies an ingredient in your food (usually proteins) as a threat.

It sets up a defense system and releases antibodies to fight the invading protein.1 These antibodies can cause an allergic food reaction.

Food Allergy Symptoms

The symptoms of food allergy can show in different parts of the body. Sometimes these signs show all at once.

Mild to moderate symptoms of food allergy include:

  • Rash or hives and itchiness in the skin
  • Swelling of the lips or face
  • Itchy and watery eyes
  • Runny nose
  • Stomach upset
  • Vomiting
  • Diarrhea

What is Food Intolerance?

Food intolerance is your digestive system’s sensitivity to certain foods. When you eat foods you’re intolerant to, this adverse reaction is triggered hours later. 

However, you have to ingest plenty of these foods before your symptoms appear.2

What Causes Food Intolerance?

Food intolerance happens when something in your food irritates your digestive system. It occurs when your stomach can’t digest or break them down properly.3

More often than not, people with food intolerances lack the digestive enzymes to break down their foods or a specific ingredient.

For example, people with lactose intolerance lack the enzyme lactase. Lactase helps digest lactose in dairy products.

Food Intolerance Symptoms

The symptoms of food intolerance typically affect your digestive system. 

These are the signs you may have food intolerance:

  • Stomach pain
  • Flatulence or gas cramps
  • Bloating
  • Vomiting
  • Heartburn
  • Diarrhea
  • Headache
  • Nausea
  • Irritability or nervousness

What Are The Most Common Food Allergies?

Food allergies are increasingly common nowadays. But treatments are not yet available. 

Knowing which particular foods to avoid is an excellent way to prevent a food allergy. You can scan for them on food labels.

The United States Food and Drug Administration (FDA) identified eight major food allergens. Most people are commonly allergic to these foods:4

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

These foods account for 90% of all the food sensitivities and severe allergic reactions in America. 

Other foods that people may be less commonly allergic to are those that contain gluten, such as wheat, barley, rye, and sesame.

The FDA prioritizes the health of consumers with food sensitivities and health conditions like celiac disease. This is why they set a standard for “gluten-free” in food labeling.

The FDA also considers color and food additives added to drugs and make-up as allergens since some people may be hypersensitive to them.

What Are The Most Common Food Intolerances?

Food intolerance has less serious symptoms than a food allergy. Ingredients in foods and naturally occurring chemicals can cause intolerances. 

Foods and ingredients that people are commonly intolerant to are:

  • Lactose
  • Histamine
  • Gluten

Do You Have Food Allergies or Food Intolerance?

A mild to moderate food allergy may appear as food intolerance because of its symptoms. But there are other signs you can observe to tell them apart. 

The symptoms of a true food allergy appear almost immediately. Usually, they occur a few minutes to two hours after being exposed to a food allergen. 

"Since we consume foods by mouth, the initial allergic reaction typically involves your mouth, lips, and throat. This is called an oral-allergy syndrome," says Dr. Mira.

A food intolerance shows up within 30 minutes to 48 hours after your last meal.

"The symptoms of food intolerances arise because the body tries to get rid of the allergen. Patients with food intolerance usually vomit or experience loose stools," explains Dr. Mira.

A severe food allergy can be dangerous and life-threatening. But with food intolerance, the symptoms are less serious.

Signs You Have Severe Food Allergies

A food allergy can have severe symptoms. Anaphylaxis is a life-threatening sign of a severe allergic reaction. 

Symptoms may include one or more of the following:5,6

  • Difficulty breathing
  • Swollen tongue
  • Tightness of the throat
  • Difficulty talking
  • Hoarse voice
  • Wheezing
  • Persistent cough
  • Persistent dizziness
  • Losing consciousness
  • A drop in blood pressure

Young children with anaphylactic shock may suddenly turn pale and floppy.

Many factors influence how severe your anaphylaxis is. This includes the amount of food ingested and how the food was prepared and eaten.

"Persons who have a history of anaphylaxis are also are more prone to have another bout of severe reactions," says Dr. Mira.

A person suffering from a severe allergic reaction will need urgent medical care. This is to relieve symptoms and avoid further complications.

How to Test for Food Allergies and Intolerances

Some people know which foods cause their allergies or intolerances. On the other hand, others may need medical intervention to find what’s causing them.

According to Dr. Mira, the gold standard for diagnosing food allergies is an oral food challenge test. However, she says it is costly, time-consuming, and risky.

Thankfully, there are board-certified allergists who can help diagnose your condition with the following measures:

Elimination Diet

The elimination diet is a special diet to test for food allergies and intolerances. Your allergist will ask you to keep a daily journal of the foods you eat, as well as the medications you take.7

You’ll also write down the symptoms that show each day. Next, your doctor will ask you to avoid suspected foods for one to two weeks.

If your symptoms decrease when you stop eating certain foods, they are likely triggering your allergies or intolerance.

However, you’ll have to decide with your doctor on which foods to avoid, for how long, and when you can eat them again.

Skin Prick Test

The skin prick test is among the standard tests for food allergies. It gives fast results, usually in 15 to 30 minutes.

A small drop of allergen solution will be placed on your forearms. Then, they’ll use a sterile lancet to prick through the allergen carefully.8

Once the allergen penetrates the outer layer of your skin, it’ll trigger a response. An itchy, red bump (wheal) will appear in 15 minutes if you’re allergic to the substance.

Keep in mind that the wheal’s size doesn’t predict the severity of your reaction to an allergen.

Blood Test

A blood test can also determine if you have food allergies and sensitivities. The results may take several days to arrive.

Healthcare professionals usually perform it on people who aren’t qualified to take a skin prick test because they have skin reactions like rashes, hives, and so on. 

The doctor will test your blood for Immunoglobulin E (IgE) antibodies. The immune system releases these antibodies during an allergic reaction. 

Remember that the level of IgE antibodies responding to an allergen doesn’t predict how severe your allergic reaction will be when exposed to it.

Food Sensitivity Tests

Most people produce Immunoglobulin G (IgE) after eating food. IgG levels may increase when you’re exposed to foods you have intolerance to.

Tests that measure your IgG can help you find out if you have a food sensitivity. They typically check how your IgG antibodies react to different foods.

We have a list of the best food sensitivity tests that you can choose from. They can test for dozens (and sometimes hundreds) of foods.

They can help you narrow down foods that you may want to avoid or watch out for. Just make sure to check with your doctor so they can guide you on the next steps.

Updated on January 31, 2024
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8 sources cited
Updated on January 31, 2024
  1. Food Problems: Is it an Allergy or Intolerance.” Cleveland Clinic.
  2. Overview: Food Allergy.” National Health Service.
  3. Food Allergy vs. Intolerance: Know the Difference.” Canadian Society of Intestinal Research.
  4. Food Allergies.” U.S. Food and Drug Administration.
  5. Food Allergy and Intolerance.” The Better Health Channel, Victoria, Australia.
  6. Food Allergy & Intolerance Definitions.” Montana State University.
  7. Food Allergy Testing and Diagnosis.” American College of Allergy, Asthma, & Immunology.
  8. The Skin Prick Test Information for Patients.” Oxford Radcliffe Hospitals.
Dr. Rizza Mira
Dr. Rizza Mira
Medical Reviewer
Dr. Rizza Mira is a medical doctor and a general practitioner who specializes in pediatrics, nutrition, dietetics, and public health.

As a pediatrician, she is dedicated to the general health and well-being of children and expecting parents. She believes that good nutrition, a healthy lifestyle, and prevention of illness are key to ensuring the health of children and their families.

When she’s not in the hospital, Rizza advocates and mobilizes causes like breastfeeding, vaccination drives, and initiatives to prevent illness in the community.
Cristine Santander
Cristine Santander
Content Contributor
Cristine Santander is a content writer for KnowYourDNA. She has a B.S. in Psychology and enjoys writing about health and wellness.
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