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If you avoid certain foods because your body reacts to them, you're not alone. It's estimated that 4 per cent of Canadian adults and 6 per cent of children suffer from food allergies, a number that's on the rise.

People with food allergies must avoid certain foods and scrutinize ingredient lists to make sure packaged foods are safe for them. For some, accidentally consuming even one bite of the wrong food can be life-threatening.

During an allergic reaction, certain proteins in the offending food cause the body's immune system to react by releasing chemicals such as histamine. Histamine can trigger swelling, hives, eczema, nasal congestion, wheezing, asthma, nausea and vomiting. Symptoms usually develop within a few minutes to one hour after eating the food.

Anaphylaxis is a severe allergic reaction that occurs rapidly, can involve only a trace amount of food, and affects the whole body. Without immediate attention, death can result.

Milk, eggs, peanuts, nuts, soy, wheat and fish account for the vast majority - 95 per cent - of food allergies. Sesame seeds and certain fruits and vegetables can also trigger allergic reactions.

Sulphites, chemicals used to maintain colour, prolong shelf life and prevent bacterial growth, can also cause severe reactions in people who are sensitive to them. Although sulphites don't trigger a true allergic response, sensitive people may experience nausea, stomach pain, diarrhea, seizures, asthma and anaphylactic shock. Some people with asthma are extremely sensitive to sulphites.

Food allergies should not be confused with food intolerances, reactions that don't involve the body's immune system or the release of histamine. In lactose intolerance, for example, the body does not have enough of the enzyme lactase, making it difficult to digest the milk sugar lactose. Bloating, cramping, diarrhea and gas can result.

Unlike people with food allergies, people with a food intolerance may be able to consume a small portion of the food without symptoms. But if you have a true food allergy, even small amounts of the food will cause your immune system to react.

Experts believe that the number of people with food allergies is rising, as is the number of foods to which they become allergic. One popular explanation is the "hygiene hypothesis." This theory states that keeping children and our environment germ-free increases the body's susceptibility to allergy by altering its immune system. It's thought that a healthy immune system needs early exposure to micro-organisms to develop properly.

Our global food supply may also play a role by exposing us to foods we've never had before. Kiwi allergies are now increasingly diagnosed in North America, as are peanut allergies in countries that have introduced peanut butter.

Food manufacturing might also be to blame. Dry-roasting peanuts, common in North America, increases their allergic potential compared to boiling or frying.

If you have a food allergy, the only way to know if a food is safe is by reading the label. Yet reading labels can be frustrating. A voluntary warning of "may contain traces of peanut " means it's impossible to know whether a food accidentally contains the allergen. What about other packaged foods that don't pose such warnings? Are they safe to eat?

Label reading is expected to become easier for Canadians. New regulations announced in July will require food manufacturers and importers to declare food allergens on ingredient lists. Tree nuts, peanuts, sesame seeds, wheat, eggs, milk, soy, shellfish, fish, sulphites - and their derivatives - will be disclosed as an ingredient or in a statement following the ingredient list. Manufacturers have one year to comply with these new labelling rules.

Under current regulations, food manufacturers must list ingredients that are added to a food. But a food allergen may remain unlisted if it's a component of an ingredient. Health Canada allows close to 50 ingredients - including flour, starches, butter and margarine - to be listed without mentioning the components. Under the new rules, ingredient components will be listed in the case of some food allergens such as whey (a milk protein added to margarine) and wheat (sometimes used to make modified food starch).

While waiting for labels to become more precise, the following strategies can help minimize the risk of an allergic reaction.

Read ingredient lists every time

Become familiar with terms on ingredient lists that indicate allergenic foods. For example, if you're allergic to milk protein, foods made with casein, whey and lactalbumin must be avoided. Because manufacturers often change ingredients, always read labels even for products you've purchased before.

Ask about ingredients

When dining out, ask whether the dish contains the specific food you are allergic to and how the food is prepared. While a dish may not contain peanuts, the fact that it's fried in peanut oil might be overlooked. If the server is unsure, ask the chef.

Avoid cross-contamination

If you must keep food allergens in your home, keep them far from food preparation and serving areas. Use separate cooking equipment and utensils; thoroughly clean work surfaces that have touched allergenic foods.

Be prepared

If you have food-related anaphylaxis, do not eat if you do not have your epinephrine auto-injector. Carry it with you at all times.

Leslie Beck, a Toronto-based  dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday.