What Causes Food Allergies? (video/podcast)

Most people don’t think of food they eat as dangerous, but if you’re allergic to something you eat, the consequences can be very serious. Food allergies develop when the immune system inappropriately reacts to a specific food because it thinks that food is harmful. It releases allergic antibodies to protect the body, which leads to food allergy symptoms ranging from a skin rash or abdominal pain to potentially life-threatening breathing problems.

In this video, San Diego Health host Susan Taylor discusses food allergies and how to manage them with Hannah Wangberg, MD, an allergist and immunologist at Scripps Clinic Carmel Valley and Scripps Clinic Rancho Bernardo.

Food allergy is often confused with food intolerance, also known as food sensitivity, but they are not the same.

Food intolerance does not involve the immune system; a person may have bothersome symptoms, such as an upset stomach, bloating or headache when they eat a certain food, but they’re not at risk of having a life-threatening allergic reaction. Similarly, lactose intolerance, gluten intolerance and celiac disease are forms of food intolerance, but they are not food allergies.

Food allergy symptoms usually occur within minutes of eating and may be mild, moderate or severe.

“Often, patients have skin symptoms, such as itching or hives. They may have abdominal pain, vomiting or diarrhea,” says Dr. Wangberg. “Anaphylaxis, a very serious allergic reaction, can involve multiple organ systems with symptoms, such as hives, vomiting and difficulty breathing.”

Food allergies can affect anyone at any age, from infants to adults. While no one is born with food allergies, the tendency to develop them can be present at birth. Parents often begin giving their infants food at around six months, so these allergies can show up at a very young age.

Having a family history of allergic conditions is a risk factor for developing food allergies.

“Asthma, eczema, seasonal allergies, all of those in the family history can raise an individual’s risk,” says Dr. Wangberg. “We know that infants and toddlers who have eczema are also at higher risk of food allergies.”

Certain foods are more likely to trigger the immune system than others. Many people have heard of food allergies caused by peanuts, but other common foods high on the allergy list include tree nuts like cashews and walnuts, milk, eggs, fish, shellfish and soy.

If you consistently have hives or other reactions after eating certain foods, it’s a good idea to make an appointment with your doctor. In addition to improving your quality of life, identifying food allergies can help protect your health and reduce inflammation in the body.

A food allergy diagnosis often begins with a skin test, also known as a skin prick test. During the test, a small amount of a potential food allergen is placed on the skin, and the skin is then pricked with a small device. If you are allergic to the food, a raised, red, itchy bump called a wheal will appear at the test site within 15-20 minutes. 

Alternatively, blood testing may be used to diagnose food allergies. A blood test for food allergies, called an ImmunoCAP test or a RAST test, measures antibodies in the blood produced when a food is consumed.

Once you have identified problem foods, you can eliminate them from your diet.

“We often see improvement in symptoms quickly after you eliminate the food. You stop having these significant allergic reactions, and we often advise avoidance of the food moving forward,” says Dr. Wangberg, adding that the same is true with food intolerance.

In addition, you’ll likely work with an allergist to create an allergy action plan.

“We teach people how to recognize the symptoms of the allergic reaction and train them how to treat a severe allergic reaction,” she says. “Sometimes we give them a drug that’s injected into their leg or sprayed into their nose. Creating an allergy action plan is very important if you have a food allergy.”

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