Food Allergy vs. Food Sensitivity: What's the Difference?

A food allergy is an immune response to a food that can cause symptoms ranging from a minor rash or hives to a life-threatening allergic reaction known as anaphylaxis. Food allergies are not the same as food sensitivities. A food sensitivity is also an immune reaction, but it is more likely to cause digestive problems, such as heartburn or bloating. Also, symptoms of food sensitivity can be delayed for two to three days, unlike a food allergy, which has immediate results.

In this article, we will briefly go over the differences between a food allergy and a food sensitivity, including how they present, how to determine which one you may have, and how they can be managed. 

They Are Not the Same! 

There’s a big difference between a food allergy and a food sensitivity. A food allergy is an IgE-mediated immune response. IgE is a type of antibody that is linked with allergic reactions and the rapid immune response. A food allergy causes an immediate reaction upon exposure to the food.

Depending on the allergy, you can see multiple organs and regions of the body affected, and even the smallest exposure to the trigger food can cause a reaction. For example, someone with a severe peanut allergy may have an immediate reaction just by inhaling a tiny amount of peanut dust. Food allergies have the potential to be life threatening when they lead to anaphylactic shock. (Source)

In comparison, a food sensitivity presents differently. A food sensitivity is an IgG-mediated immune response. Specifically, the immune system builds up the amount of the IgG antibody over time, as it is repeatedly exposed to the same trigger food. It is a delayed immune response that may occur as quickly as 1 hour or as long as 48 hours after the trigger food is ingested. (Source) 

Like food allergies, food sensitivities can also impact multiple areas of the body besides the digestive tract. You are also more likely to have a reaction if the trigger food is encountered frequently or in large amounts. A food sensitivity is more difficult to diagnose than a food allergy, and it is often overlooked or misdiagnosed. (Source)

How Do I Know Which One I Have? 

Signs and Symptoms of Food Allergy

A food sensitivity and a food allergy may have similar symptoms. However, food sensitivities usually aren't as severe as food allergies.

Food allergy symptoms can be very serious and affect multiple regions of the body, including: 

• itching
• swelling of the lips, tongue or throat
• hives (itchy red rash) 
• vomiting
• diarrhea
• stomach cramps
• severe dizziness
• fainting
• trouble breathing
• loss of consciousness
• anaphylaxis 

Anaphylaxis needs immediate attention as it can be life-threatening. (Source)

Signs and Symptoms of Food Sensitivity

Food sensitivity symptoms can be hard to distinguish from symptoms of other conditions. For example, a food sensitivity can cause symptoms of irritable bowel syndrome (IBS). Although the symptoms are similar and IBS may be affected by diet, it is a completely different kind of disorder.

A food sensitivity may be hard to recognize, as symptoms don’t always appear right after eating. Therefore, it can be hard to know exactly which food caused your associated symptoms.

Food sensitivity symptoms are commonly isolated to the gut, including: 

• bloating 
• nausea
• indigestion
• diarrhea 
• constipation

However, you may also notice symptoms that affect other areas of the body, including:

• fatigue 
• brain fog
• migraines
• skin rashes
• hair loss

(Source, Source)

Testing for Food Allergy and Food Sensitivity

To properly treat a food allergy or a food sensitivity, you first need to know which one you have. There are blood tests available to help tell the difference, but they are not all equally useful.

Serum IgE for Food Allergy

The test for a food allergy is called a serum IgE test. IgE is a type of antibody. When you have a food allergy, your immune system produces too much IgE in response to a trigger food. (Source)

Serum IgG for Food Sensitivity

Unfortunately food sensitivity testing, or IgG testing, is often unreliable, either giving false positive or false negative results. Therefore, it is not useful when trying to identify trigger foods. (Source) 

Elimination Diet for Food Sensitivity

The best solution may simply be to avoid the food you are sensitive to. This can be difficult, because it involves breaking habits and avoiding foods that are part of your regular diet.

An elimination diet is the most accurate way to figure out if you have food sensitivities and is considered the gold standard. Some common elimination diets include the AIP (autoimmune protocol) diet, low-FODMAP (fermentable oligo-, di-, mono-​saccharides and polyols) diet, or specific carbohydrate diet (SCD). (Source) 

Even though a food sensitivity can be more difficult to recognize, symptoms are often relieved once the source is identified and eliminated. 

Additional Tips 

• Don’t ignore early symptoms. Food allergy symptoms may start off mild and quickly become life threatening. You can’t always foresee how severe an allergic reaction will be, so it’s important to act quickly. (Source)
• Educate yourself. Pay attention to the ingredients of the food products you’re buying. Some of your favorite foods may contain ingredients you’re not aware of. (Source)
• Keep a food journal. The purpose of a food journal is to identify and track the foods that trigger your symptoms, so you can avoid or limit them. It‘s helpful to record exactly how you feel after eating certain foods. (Source) 

The Bottom Line on Food Allergy vs. Food Sensitivity 

Although food allergies and food sensitivities are both immune-mediated responses, they present differently. A food allergy typically initiates an immediate response, while the response to a food sensitivity is usually delayed. Tests for food allergy may be reliable, but an elimination diet may be more effective for diagnosing food sensitivity. Understanding the different types of food reactions may help you identify food(s) that trigger your symptoms.