Food Allergy vs Intolerance: What’s the Difference?


Your son has a peanut butter and jelly sandwich for lunch and 10 minutes later has hives around his mouth. Your daughter eats a bowl of ice cream and a couple hours later complains of a bellyache. Both scenarios can be reactions to foods – but are they allergies or intolerances?

This is a question that I answer frequently in our allergy clinic, and it’s important to understand the difference between the two. The terms intolerance and allergy are often used interchangeably, but they’re indeed quite different: one can cause mild to moderate symptoms, and the other can be potentially life-threatening.

Food Allergy
I find the easiest way to explain the difference between the two is to start with food allergy. Food allergies are defined as an immunologic (or immune system) response to eating a specific food. When the offending food is eaten, the body thinks that it is harmful and will produce antibodies called immunoglobulin E (IgE) to defend against it, producing an allergic reaction. The symptoms of an allergic reaction can range from mild to life-threatening and can occur anywhere on the body and happens fast, usually within 20 minutes. Additionally, when your child is allergic to a specific food, he will have a reaction every time he eats it, although the amount that will cause a reaction may vary, from a trace amount to a full serving.

Food Intolerance
On the other hand, food intolerance is a reaction that happens during the digestive process and is NOT life threatening. Common symptoms include gas, cramping and bloating. When your child has an intolerance to a particular food, it can take hours for her to notice symptoms as the food has to go through the digestive process before symptoms are felt. Typically there is a “tipping point” with food intolerance. Your child may be able to eat a little amount of the offending food without having symptoms; however, at some point she’ll start having symptoms if she eats it more frequently. For example, she might not be able to eat cheese with every meal, but she can have a small amount once a day.

Here is a handy chart that sums up the difference between food allergy and intolerance:

The bottom line is that food allergies need to be taken very seriously. If you suspect your child has a food allergy, start with your pediatrician. She may recommend your child be evaluated by an allergist. If your child has a known food allergy, please keep his injectable epinephrine with him at all times.

On the other hand, food intolerances, while not life threatening, can certainly cause discomfort. They can be difficult to recognize in children because you have to notice the pattern of symptoms and narrow down the offending food. The most common food intolerance is lactose intolerance, which is the body’s inability to digest the sugar found in milk. Fortunately there are lactose free milks that you can try. If you suspect your child has a food intolerance, please have a conversation with your pediatrician before altering his diet.

Dr. Amal Assa'ad

About the Author: Dr. Amal Assa'ad

Dr. Amal H. Assa'ad is the director of clinical services in the Division of Allergy and Immunology and associate director of the Division of Allergy and Immunology.

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  1. Laurie Jones January 24, 09:31
    Please add an EGIDS column to that helpful chart. As hard as it is for many non allergic people to understand real allergies, it is even harder for people to understand gastrointestinal allergies. It is not life threatening, but it requires an invasive endoscopy to determine if level of illness, and could result in remodeling of the esophagus making food unable to pass. Allergy symptoms it shares can be : trouble swallowing, chest pain (esophagus - but hard for young children to determine), can happen quickly after eating food, can happen every time the food is eaten, may need to a little of food, symptoms shared by both allergy and intolerances: can cause vomiting and diarrhea. And it share most of the symptoms in the intolerance list. It is a complicated disease that is very hard to manage, many people have to be fed a special formula while they are trialing foods. Most people have never heard of it. Often Drs know very little about it. It is very difficult for parents of school age children. They always have to fight for their children to be accommodated. At this point in research it is considered an allergy and it is distressing that it was not included in your chart.
    • Rachel Camper
      Rachel Camper January 27, 08:47
      Hi Laurie, Thanks for the suggestion! You're right: EGIDS has a complex relationship with food allergens and can often be confusing for both patients and physicians. Because it's such a complicated topic, we plan to do a separate post about EGIDS in the future.
  2. dean marion September 30, 11:52
    dean love it