Food Allergy Vs. Food Intolerance: Not Every Reaction To Food Is An Allergy

by Elaine Roth
Originally Published: 
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Not long ago, I met a friend at a restaurant for dinner. Before she ordered, she told the waiter that she was allergic to a specific food. The waiter confirmed that the dishes she’d ordered weren’t cooked or garnished with that food.

After the waiter walked away, she explained that the food upsets her stomach most times that she eats it, so she’d started to avoid it. As she no doubt should. However, my friend does not have an allergy. Like so many folks, she conflated the term food allergy with the term food intolerance.

A food intolerance is certainly a valid reason to request a particular item be held back, but it’s not the same thing as a food allergy.

Scary Mommy spoke with Dr. Wendy Sue Swanson, MD, MBE, FAAP, pediatrician and Chief Medical Officer, SpoonfulONE, about the difference between a true food allergy versus a food intolerance, and why that distinction matters.

A True Food Allergy Is An Immune Response

A true food allergy is a dysfunction of a very specific part of the immune system. The immune system does the wrong thing, according to Dr. Swanson, and that can lead to severe and life-threatening consequences. On the other hand, a food intolerance is located in your digestive system. It’s an episodic, inconsistent discomfort.

In a food allergy, the body’s IgE reacts to normal proteins, such as milk, eggs, or tree nuts. The body activates and creates a response. In infants, and toddlers that response is most commonly hives or vomiting. In older children and adults, the response can become more severe.

A food intolerance is unrelated to the body’s immune system. It can be caused by a lack of enzyme (like a lactic enzyme). It’s often associated with discomfort in the GI tract, such as bloating and gas.

Food Allergy Symptoms Are Different From Food Intolerance Symptoms


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The symptoms of a food allergy are very different from those of a food intolerance. Food allergy symptoms range from uncomfortable to life threatening and they occur every time the food is eaten. Food allergy symptoms can affect a number of organs in the body. They include: rash, hives, itchy skin, shortness of breath, swelling, trouble swallowing, chest pain, nausea, diarrhea, vomiting.

In infants, a typical food allergy reaction is hives or vomiting within minutes to two hours of eating the food. Luckily, infants rarely experience anaphylactic reactions to foods, confirms Dr. Swanson.

In terms of infants, it’s important to note that “eczema is the number one risk factor for developing a food allergy,” says Dr. Swanson. This is related to the way the allergen is introduced—through skin rather than through digestion.

A food intolerance is usually limited to the digestive system. It is not life threatening and its frequency differs. The response isn’t consistent each time the food is eaten. The symptoms include: gas, cramps, bloating, heartburn, headaches, irritability, nausea, diarrhea, vomiting.

Food Allergies Must Be Managed With Great Care

Dr. Swanson highlights that the main reason the distinction between food allergies and food intolerances matters is this: “food allergies need to be managed with great care.”

Once a food allergy is developed, the symptoms can advance through life, according to Dr. Swanson. There is no cure for a food allergy. Patients are advised to avoid the food entirely. There is some positive news, however. Researchers have developed treatments that help patients develop a tolerance for food that would otherwise cause a reaction. The treatments are “kind of like a bandaid,” notes Dr. Swanson, rather than a cure.

In terms of treatment, a food intolerance is similar to a food allergy in that the suggested strategy is prevention—avoiding the food. However, because the symptoms tend to be inconsistent, intermittent, and less serious, there’s less risk if the food is eaten.

Food Allergies Are Diagnosed Through Testing

Food allergies can occur at any time, including in adulthood. Typically, food allergies are diagnosed through testing. Allergy specialists will conduct a skin test or a blood test to determine the body’s response to a specific food. The “gold standard” for food allergy testing is an oral test, notes Dr. Swanson. During this kind of test, the patient eats the food in the presence of an allergist who can monitor the results.

Food intolerances are typically diagnosed either by symptoms (like in the case of a lactose intolerance) or by avoiding the food in question and seeing how the body feels. Food intolerances can occur at any time. Some intolerances, such as a lactose intolerance, usually don’t occur in infancy. According to Dr. Swanson, a lactose intolerance is an inheritable intolerance that occurs with age, as the patient loses the ability to produce the enzyme required to breakdown lactose.

It’s easy to characterize any reaction to food as an “allergy.” However, an allergy is a very different thing, which often comes with severe or life-threatening symptoms. “One is dangerous and one is not,” notes Dr. Swanson, but both should be taken seriously by a medical professional.

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