The Truth About Food Allergies
Confused by new government guidelines? Can’t tell what’s myth or fact? We set you straight.
If you are among the 7.6 million Americans who have a food allergy, you know that buying groceries and eating out can be a minefield. How do you know if what you’re about to eat will trigger a reaction? For some people, a culprit food may cause a life-threatening response called anaphylaxis, a severe lowering of blood pressure that can result in death. Though food allergies are most common in children, adults can get them, too. Here, Dr. Hugh Sampson, of Mt. Sinai School of Medicine in New York City, one of the primary authors of the National Institute of Allergy and Infectious Diseases’ recently updated guidelines for the Diagnosis and Management of Food Allergy, answers common questions about adult food allergies.
What exactly is a food allergy?
It’s an adverse reaction to a food that is caused by an immune response. There are two different types. One is triggered by an antibody called IgE. It typically causes symptoms such as hives, a stuffy or runny nose, sneezing, tightness in the chest, and abdominal problems like nausea, diarrhea or vomiting, but it can also cause anaphylactic shock. Another type is called a non-IgE mediated allergy. Its mechanism isn’t clear but it usually causes GI symptoms such nausea, vomiting and diarrhea.
What are the most common allergenic foods?
The most common food allergies are to milk; eggs; fish; crustaceans such as crab, lobster and shrimp; tree nuts, like almonds, walnuts and pecans; peanuts; wheat; and soybeans.
Is an intolerance, sensitivity or deficiency the same as an allergy?
No. An allergy is caused by an immune response. An insensivity, intolerance or deficiency occurs because your body is unable to break down a substance in the food. These conditions typically don’t cause anaphylaxis. Lactose intolerance, for instance, results when you lose the ability to break down the lactose (sugar) in milk and other dairy products. It can cause GI problems like nausea, diarrhea bloating and gas. Some people can’t tolerate certain foods such as onions or garlic because their bodies can’t break down some of the substances in the food and, as a result, end up with abdominal pain or nausea.
What about gluten? More and more people seem to have problems with it.
What most people refer to as gluten intolerance is celiac disease. An inherited disease, it’s characterized by an immune response against part of the GI tract that’s provoked by foods containing gluten. People who have it need to be identified and avoid foods containing wheat, rye, barley and triticale (a cross between wheat and rye).
Can an adult develop a food allergy?
Food allergies more frequently occur in infants and children, though we certainly see adults developing them. Why that happens is really not clear.
Are people with other allergies more at risk for food allergy?
But one form of food allergy common in adults, oral allergy syndrome, is related to certain pollen allergies. People who have a spring allergy to birch pollen may develop itchiness in the mouth, swelling of the lips and tongue and tightness in the throat if they eat raw foods such as apples, pears, kiwi, carrots and potatoes. That’s because a protein in these foods is very similar to birch pollen. People who are allergic to ragweed, a common fall allergen, get the same symptoms in the autumn if they eat bananas or melons. Some people develop so much antibody to birch or ragweed that their symptoms persist all year. These people should avoid the raw form of the fruits and vegetables that cause their symptoms.
Many children outgrow food allergies. Can adults?
Food allergy hasn’t been well studied in adults. The foods that adults are allergic to are the ones that tend to persist—namely peanuts, seafood and tree nuts. Our general feeling is that most adults who develop food allergy have persistent symptoms. People with oral allergy syndrome may lose those symptoms as they get older because conditions like pollen sensitivity tend to improve with age.
What’s the best way to find out if you have a true food allergy?
See a doctor who is knowledgeable about food allergy. He or she will review your symptoms. The diagnosis of a non-IgE mediated allergy is primarily based on taking a history. If it sounds as though your allergy is IgE-mediated, the doctor will do skin prick tests or blood tests to look for evidence of the IgE antibody to specific foods. He or she may also order an oral food challenge. Prior to the challenge, you eliminate suspect foods from your diet for two to eight weeks. Under medical supervision, you eat a small dose of the food and are monitored for an allergic reaction.
Can a food allergy be treated?
No. The best treatment right now is to avoid the food. A number of therapies are being looked at in trials. But if developed, they won’t be available for regular use for at least five to 10 years. If you have an IgE-mediated food allergy, you are at risk for anaphylaxis and should carry an epinephrine injection device with you at all times. The first line treatment for anaphylaxis, it could save your life.