The facts about food allergies
Have you ever eaten a food that just didn't agree with you? Food allergies and intolerances are very common. Even as early as the fifth century BC, Hypocrites recognized that some people got sick from foods that most tolerated well. 
One in three people say they have had unpleasant reactions to foods. Yet only one to three per cent of the population actually has a clinical allergy.
Defining food allergies
Food allergies and intolerances are not the same. Although they can have similar symptoms, there is a major difference between the two. Food allergies are an immune system response, and tend to produce more severe symptoms.
When the immune system reacts to a food it creates antibodies, causing an allergy. If the same food is eaten again, the antibodies signal the immune system to release massive amounts of chemicals, including histamines. This triggers a cascade of allergic responses including asthma, rashes, mood swings, headaches, itching, swelling, hives, breathing difficulties and heart palpitations. These acute symptoms usually happen within minutes after ingestion of the food.
Some allergic responses to food are serious and even fatal, such as anaphylaxis. Anaphylaxis is a systemic reaction that involves many areas of the body including the respiratory tract and cardiovascular system. Symptoms usually occur within minutes of eating the offending food. Those with asthma, eczema and hay fever are at a greater risk.
What foods cause allergies?
While people can be allergic to any food, the following foods account for 90 per cent of all allergic reactions:
- Milk
- Fish
- Eggs
- Peanuts
- Soy
- Shellfish (especially lobster or crab)
- Wheat
- Tree Nuts (walnuts/cashews)
Children are most likely to be allergic to eggs, milk, soy, wheat and peanuts. However, you aren’t necessarily allergic to a food forever. Allergies can change or be "outgrown" because they evolve as conditions in the body alter. They can worsen, but can also disappear.
While reactions vary greatly, certain foods tend to cause more intense reactions. Reactions to soy are usually mild. Reactions to peanuts are often life-threatening. Depending on the severity of the allergy, you may need to avoid, or completely shun even the most minimal amount of the food from your diet.
Depending on the severity of the allergy, you may need to avoid, or completely shun even the most minimal amount of the food from your diet.
Non-allergic food reactions
Only reactions that trigger immune system responses are true allergies. Unlike allergies, food intolerances are common and usually caused by a lack of enzymes needed to digest food. People with lactose intolerance, for example, lack the enzyme lactase, needed to digest milk sugar. Reactions include bloating, gas and abdominal cramping and pain.
Intolerance to gluten—the protein in grains like wheat, oats, rye, and barley is also widespread and triggers similar reactions. The reactions of food intolerance can be delayed for hours or even days after eating the substance.
Diagnosing food allergies
Many people self-diagnose food allergies, but clinical tests show that they are frequently wrong. While food allergies affect about three per cent of the population, surveys of self-diagnosed allergies show that many more believe they are allergic.
Keeping a detailed food diary is a good first step to determining a true allergy. Record what you eat at meals and snacks, the symptoms experienced, and the timing of both. A skin test may be useful to measure reactions to particular foods or to show that an allergy does not exist.
Generally, a positive skin test is less consistent than a negative. Other tests like the RAST and ELISA measure the levels of antibodies in the blood. These tests can be good initial indicators of an allergy but can also be undependable, since people can have antibodies to foods, without suffering an allergic reaction.
Eating choices for food allergies
There are no cures for food allergies. The only way to prevent reactions is to avoid the trigger foods. This means becoming an expert food label reader—and even this skill doesn't guarantee that reactions won’t happen. The Journal of Allergy and Immunology found that 50 per cent of reactions to foods were hidden in sauces and dressings, and 43 per cent were caused by desserts.
Check the labels on your favourite foods on an ongoing basis. Ingredients are always changing. Food labels can also be inaccurate. Stay up to date through allergy networks and Web sites. Consider foods you may not have thought of as part of your regular diet. Looking into new flavours and choices may enhance your choices and even your health.
When dining out, don't be afraid to quiz the waiter about how your food is prepared and make him or her aware of your allergies. Across Canada, 1800 restaurants, including nine national chains, are now participating in Allergy Aware. This program provides diners with information on common allergies and menu item ingredients. Look for the Allergy Aware symbol in restaurant windows. Many with allergies also carry epi-pens, in case a life-threatening reaction should occur.
Allergies are a part of life for many people and can cause frightening and sudden symptoms. Gather as much information as possible and make choices that ensure continued enjoyment of as many foods as possible.