Food Allergies

Food allergies are often misunderstood. Oftentimes, what is at first thought to be a food allergy turns out to be something else. For example, many people think they are allergic to a food when in fact they have a food intolerance, a much more common cause of symptoms such as nausea, cramps and bloating. The difference is that intolerance symptoms are not triggered by an immune system reaction, as is the case with allergies. People with lactose intolerance, for example, lack an enzyme needed to digest the sugar (lactose) in milk. A closer look at the basics of food allergy may help clear up the confusion surrounding the problem.

The Typical Food Allergy

Let’s look first at "true." or "typical" food allergies and how to avoid them. An allergy is caused by an immune system reaction to an allergen (any protein that causes an allergic response, in this case proteins in certain foods). The immune system produces allergy antibodies (IgE) to these food proteins, so that the body recognizes the food as a foreign invader(much as it would a parasitic infection.) If you have developed a food allergy, any time you eat the offending food, your body will launch a defense, releasing chemicals, such as histamine, that trigger your symptoms. Classic food allergies include reactions to milk, soy, egg whites, shellfish and peanuts. Peanut allergy is a good example to examine, since it is one of the most widely known food allergies and is becoming more common. It is also the food allergy most likely to be fatal. Food allergy symptoms can range from hives and itchy skin to potentially deadly reactions such as airway constriction, throat closing or complete anaphylactic shock.

One question frequently asked of me is whether people can outgrow their food allergies. The answer is both yes and no. Between 6 and 8 percent of children younger than 3 will experience a food allergy, yet many will out grow them by the age of 10. While I see this frequently with egg and milk allergies (about 90 percent to 95 percent of the time), it is much less common with nut allergies, Only about 30 percent of children will lose their allergy to peanuts.

Food Allergy Reactions

Reactions that may indicate a food allergy are itchy mouth, "fullness" in the throat, difficulty breathing, an intense, itchy rash associated with or without urticaria (hives) and angiodema (swelling), and vomiting. In a worst-case scenario, a food allergy can result in anaphylaxis, a serious, sometimes life-threatening, reaction that may include airway constriction, a drop in blood pressure and loss of consciousness. Although severe reactions do occur, milder food reactions are more typical. Common mild reactions would include hives or red, itchy skin (eczema). Some of my patients with mild food allergies have also complained of fatigue or increased nasal irritation.


When I evaluate patients for food allergy, I pay close attention to the timing of their symptoms. Food allergy reactions usually occur within minutes, and sometimes within seconds, of eating the offending food. So when a person says he or she ate a certain food yesterday and has itchy skin today, this reaction is probably not due to a food allergy.

To help discern which food may be the problem, some doctors ask patients to keep a food diary, recording their eating habits and any symptoms that arise. When you’ve arrived at a culinary suspect or two, your doctor may have you start an elimination diet, which involves removing the foods from your diet for a short period, then gradually reintroducing them, one by one. This process may pinpoint the offending food. The best diagnostic tools for food allergies, however, are skin testing and blood testing. In skin testing, the offending food is lightly scratched into the skin with a disposable plastic "scratcher." If you are allergic, the area gets red and itchy. Its advantages are that the test results are ready within 20 minutes, and it is cheaper than blood tests. However, a blood test actually measures the presence of certain allergy-related antibodies in your bloodstream. It is helpful in confirming results from skin testing, especially in individuals who have a rash that would complicate a skin test. The results of the blood tests should be evaluated by an experienced allergist.

Managing Food Allergies

I always equip my patients with a game plan to follow in case they accidentally eat something they shouldn’t. This includes having an over-the-counter antihistamine, such as diphenhydramine (Benadryl), as well as an epinephrine injection kit, such as an Epi-Pen or Twinject, with them at all times. I also instruct them to go to a hospital emergency room or call 911 in case of an attack. In some more severe cases, the treatment protocol includes other medications, such as the corticosteroid prednisone, which fights inflammation. I may also recommend that people with a true food allergy wear a medical alert bracelet.


Food allergies are most easily developed when we are young. At this early stage our intestines are not fully developed, and they allow large, complex proteins such as peanut protein to react with the body. The young immune system may recognize such proteins as foreign and form antibodies against them. Therefore, it’s important to gradually introduce new foods into your child’s diet. These are good timelines:

  • 6 to 12 months: vegetables, cereal, meat, egg yolk, soy and certain fruits
  • 12 months: berries, egg white, corn, citrus and melons
  • 3 years: fish, shellfish, tree nuts and peanuts

Is it Food Allergy or Something Else?

Certain foods are often erroneously blamed for being allergenic foods when in fact they have naturally occurring histamines that may cause symptoms in some people. Examples of foods with natural histamines are:

  • Wine
  • Chocolate
  • Strawberries
  • Tomatoes

If you are sensitive to one or more of these foods, you might get an itchy rash or a headache after eating them. But if you were tested for a food allergy the results would probably be negative. The exception is wine, especially red wine, some of which is made with preservatives called sulfites and can cause rare but severe allergic reactions. (That’s why you see warnings on wine bottles about the product’s sulfite content.)

Some of my patients tell me that they are allergic to milk. However, it frequently turns out that their stomach discomfort (pain, gas and bloating) is caused by lactose intolerance. As a result, the lactose ends up fermenting in the person’s intestines. Eating yogurt or cheese and drinking lactose-free milk can help, as may supplemental forms of lactase (an enzyme that breaks down lactose) or L. acidophilus (intestinal bacteria that aid in digestion).

Some people are convinced that they are allergic to wheat and sugar, but again, it is often unclear that a true allergy is involved or that the food is the problem at all. Still, many of these people do feel better when they stop eating suspect foods. I know parents who believe that their children get fewer ear infections and are less irritable when they are off certain foods. I have also encountered a large number of people who believe that they have a yeast allergy and frequently get yeast infections. These people seem to do well on yeast-free diets and off of simple sugars (like those found in candies and chocolates).

But although food-related symptoms are often not part of a allergic response, always remember that real food allergies can be dangerous. Any potential food allergy should be diagnosed and treated by an allergist.