How To Know If You Have A Food Allergy

At Westchester Health, many patients come to us who think they may have a food allergy, or a food intolerance, or maybe both. To get the facts, and some answers, we refer them to one of our allergists who perform specific tests to determine what is causing the reactions. If it is determined that they do indeed have a food allergy, our specialists work with them to develop a diet and treatment plan so that a severe allergic reaction can be avoided.

Although 1/3 of people either say that they have a food allergy or suspect that a family member is food allergic; in fact, only about 5% of children have clinically proven allergic reactions to foods. In teens and adults, food allergies occur in about 4% of the total population.

What are allergies?


James Pollowitz, MD, FAAAAI, FACAAI

Food allergies are different from food intolerances. A food allergy is caused by a reaction by the patient’s immune system. People who are genetically predisposed can produce allergy antibodies (i.e. IgE antibodies) after initial exposure, and when re-exposed to a food, they can have symptoms such as itching, rash/hives, coughing, wheezing, throat tightness, vomiting, diarrhea or even loss of consciousness and death.

These immediate type of allergies generally produce symptoms within minutes to 1 hour after the food exposure. Food intolerances result from digestive issues, including the inability to process sugars such as lactose (i.e., lactose intolerance). Toxins in foods or bacteria can also cause food reactions which are not allergic.

Allergies can be dangerous

Since food reactions can cause serious or even fatal reactions, it is important to confirm and identify the specific food sensitivities. Here are tips that can help you find out if you’re allergic.

Which food allergies are most common?

In adults, the most common food allergies in adults include:

  • peanuts (one of the main foods that causes severe anaphylaxis, a sudden drop in blood pressure that can be fatal if not treated quickly)
  • tree nuts such as walnuts, cashews and almonds
  • shellfish (especially crustaceans such as shrimp, crayfish, lobster and crab)
  • fish
  • seeds such as sesame

In children, the food allergy pattern is different. The most common food allergens that cause problems in children are:

  • milk
  • eggs
  • peanuts
  • nuts
  • seeds
  • wheat
  • soy

In adults, allergies usually do not go away but children can sometimes outgrow them. However, they are more likely to outgrow allergies to milk, eggs or soy than to peanuts, fish or shrimp.

It’s better to see an allergist than to try to diagnose a food allergy yourself

Why is this? One reason is that if you think you’re allergic to a certain food, you’ll stop eating it. If you are wrong, you’re skipping something that might contain important nutrients, such as nuts or milk.

An allergist can pinpoint if you are truly allergic or if you merely have a food intolerance. That difference is important. Intolerances can be uncomfortable and hard to live with, but allergies can be life-threatening. Also, it may take more than one test to get an accurate diagnosis.

A third reason is that allergies could cause worse reaction with the next exposure.  Mild itching or hives could evolve into more serious problems, such as severe swelling of the throat or even going into shock (anaphylaxis).

Finally an allergist, he/she can prescribe medications to treat your symptoms. This may include an epinephrine injector, which can stop a life-threatening reaction.

Questions an allergist might ask you

To diagnose a food allergy, an allergist must first determine if the patient is having an adverse reaction to specific foods. This assessment is made with the help of a detailed patient history, the patient’s diet diary and/or an elimination diet.

To determine what foods you might be allergic to, an allergist may ask you the following questions:

  • What foods did you eat before you had symptoms?
  • What symptoms did you have?
  • Did the symptoms come on quickly, such as an hour after eating the food? How long did they last?
  • Have you ever had a reaction like this before?
  • Does anyone in your family have allergies?
  • Was allergy treatment successful? (Antihistamines should relieve hives, for example, if they stem from a food allergy.)
  • Do you have these symptoms every time you eat this food?
  • Did anyone else get sick? For example, if you ate fish contaminated with histamine, everyone who ate the fish should be sick. In an allergic reaction, however, only the person allergic to the fish becomes ill.
  • How much did you eat before experiencing a reaction? The severity of your reaction is sometimes related to the amount of food you ate.
  • How was the food prepared? Some people will have a violent allergic reaction only to raw or undercooked fish. Complete cooking of the fish destroys those allergens in the fish to which they react. If the fish is cooked thoroughly, they can eat it with no allergic reaction.
  • Were other foods ingested at the same time of the allergic reaction? Some foods may delay digestion and thus delay the onset of the allergic reaction.

He/she may also do skin or blood tests to see if you have been sensitized (i.e. have allergic IgE antibodies) to the suspect (or related) foods.

You may be asked to keep a food diary

This simple task can help you help your allergist figure out what’s going on with your body’s reactions. For 1-2 weeks, write down in a notebook:

  • Everything you eat
  • Any symptoms you have
  • How long the symptoms last after you eat certain foods

Eliminating foods from your diet

Allergy testing can allow us to pinpoint possible food allergies. An “exclusion” or “elimination diet” can help pinpoint the problem food(s). But remember, it’s important to do this under a doctor’s supervision because a food allergic reaction can be dangerous and even fatal.

With guidance from your allergist:

  • If you think you’re allergic to a certain food, don’t eat it for 2-4 weeks. If you don’t have any more symptoms, you probably are allergic to it.
  • To eliminate a food from your diet, read food labels to make sure it is not in packaged foods you buy or consume.
  • Be aware of restaurant items that are likely to contain your problem food. If the kitchen cannot prepare the dish without it, don’t order it.
  • Make sure that the utensils, cooking surfaces and oils used to prepare your meal are not also being used to make the food you need to avoid.
  • Keep an epinephrine injector on you at all times.

Food Challenge Test

A new technique currently being used by allergists to determine food allergies and/or sensitivities involves having a patient ingest increasing quantities of a food in our office under observation/supervision of our allergists and nurses. This procedure is call a “Food Challenge Test.” We will do this procedure when testing is negative and to prove that a patient can safely eat the tested food. This procedure can be done with foods such as peanuts, nuts, shellfish, eggs, milk and sesame.

Do you think you may have a food allergy? Please come see us.

If you think you have one or more food allergies and are worried about what effects this might have on your health, please make an appointment with Westchester Health to see one of our allergy specialists for an accurate diagnosis as well as expert guidance on how to prevent future allergic reactions. Whenever, wherever you need us, we’re here for you.

Appointment CTA

By James Pollowitz, MD, FAAAAI, FACAAI, an allergy and immunology specialist with Westchester Health, member of Westchester Health Physician Partners

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