Food Allergy vs. Food Intolerance - What's the Difference?

An intolerance to a food can often be confused with a food allergy because there is an overlap in symptoms such as nausea, vomiting, cramping, and diarrhea. Worse, some non-IgE food allergies look exactly like a food intolerance. Here’s a breakdown of the similarities and differences.

How Can I Tell if My Baby Has a Food Intolerance or a Food Allergy?

The single most important difference is that intolerances are non-immunological, meaning the immune system’s antibodies are not involved. Allergies will show up when you test for IgE, IgA or IgM antibodies. If your baby is experiencing symptoms, doctors will usually test for an allergy. 

Before testing, it helps to really pay attention to the symptoms. Intolerances primarily affect the digestive system with reactions including vomiting and diarrhea. Food allergies, on the other hand, often affect multiple organs (think lungs, skin, stomach) all at once. 

The last difference is how sensitive your baby is to the food. A true allergic reaction can be triggered by even a small exposure to a food because antibodies are very sensitive. 

Intolerances can vary based on the amount of food. If you think your baby is intolerant of soy, a teensy taste shouldn’t cause a reaction whereas it would with a soy allergy.

What Are People Intolerant TO?? 

Overall, 15-20% of people have food intolerances, whereas about 8% of people have food allergies.

One of the tricky aspects of diagnosing food intolerance is that some people are sensitive not to the food itself but to an additive or preservative in the food, or an ingredient used in the preparation of the food. That’s not the case with a food allergy so different brands, washing techniques, or preparations won’t make a difference in food allergies. (Here's an important caveat on preparation affecting egg allergies).

What To Do With a Suspected Food Intolerance

If you notice that your child frequently vomits or has diarrhea, the best advice we received is to start a food diary. If you are confused about the line between spit-up and vomit, talk to your pediatrician. They may say something fun like “vomit has to project.”

Unfortunately, there are no tests that are clinically useful in identifying food intolerances. Don’t trust companies saying they can find them. Your pediatrician may recommend an elimination diet. That’s where you try to avoid suspected foods and see if things get better. If your baby is still breastfeeding, mom may also try to eliminate certain foods, though that will only help sometimes.

When Should You Call the Doctor or Go to the ER?

Know the signs and symptoms of a food allergy. The reactions usually come on quickly. If there is any difficulty breathing, or if more than one body system seems involved (i.e. hives and vomiting), give Cetirizine (or EpiPen if you have it) and go to the ER. Remember that if you give epinephrine, you still have to go to the ER because symptoms can come back.

As a parent, you should trust your instincts. This goes for all parental concerns, not just reactions to foods. Pediatricians are your partner, so if anything seems off always call your doctor. They may be able to advise you over the phone, allay your fears, or encourage you to come in for an office visit.