Symptoms & Causes of Food Allergies

Date: 6/17/2011     Category: Food Allergies What are symptoms of food allergy?
Allergic reactions to foods typically begin within minutes to a few hours after eating the offending food. The frequency and severity of symptoms vary widely from one person to another. Mildly allergic persons may suffer only a runny nose with sneezing, while highly allergic persons may experience severe and life-threatening reactions, such as asthma or swelling of the tongue, lips or throat.

The most common symptoms of food allergy involve the skin and intestines. Skin rashes include hives and eczema. Intestinal symptoms typically include vomiting, nausea, stomach cramps, indigestion and diarrhea. Other symptoms can be asthma, with cough or wheezing; rhinitis, often including itchy, stuffy, runny nose and sneezing; and rarely, anaphylaxis, a severe allergic reaction that may be life threatening. Because these symptoms can be caused by a number of different diseases other than food allergy, your Atlanta Allergy & Asthma physician may want to examine you to rule them out as the source of your problem.

What causes my symptoms?
A food allergy is the result of your body’s immune system over-reacting to food proteins called allergens. Normally, your immune system and defense mechanisms keep you healthy by fighting off infections and inactivating proteins such as food allergens, which could potentially cause allergic reactions.

In the individual with food allergy, the immune system produces increased amounts of immunoglobulin E antibody, or IgE. When these antibodies battle with food allergens, histamine and other chemicals are released as part of the body’s immune reaction. These chemicals can cause blood vessels to widen, muscles to contract and affected
skin areas to become red, itchy and swollen. These IgE antibodies can be found in different body tissues—skin, intestines and lungs—where specific allergy symptoms such as hives, vomiting, diarrhea and wheezing are observed.

Not all adverse reactions to foods are due to allergy. Some reactions to cows’ milk, for example, are related to a deficiency of an enzyme (lactase) that normally breaks down a sugar in milk (lactose). When individuals with lactase deficiency drink cows’ milk or eat other dairy products, they may experience intestinal symptoms including stomach cramping, gas and diarrhea. This is sometimes misinterpreted as a food allergy.

Why have I developed food allergy?
Heredity seems to be the prime reason some people have allergies and others don’t. If both your parents have allergies, you have pproximately a 75 percent chance of being allergic. If one parent is allergic, or you have relatives on one side with allergies, you have a 30 to 40 percent chance of developing some form of allergy. If neither parent has apparent allergy, the chance is 10 to 15 percent.

Although food allergy occurs most often in infants and children, it can appear at any age and can be caused by foods that had been previously eaten without any problems. Finally, excessive exposure to a particular food may affect the overall rate of allergy to that food, as testified to by the high prevalence of fish allergy among Scandinavians and of rice allergy among the Japanese.

Which foods are most likely to cause allergy?
Eggs, cows’ milk, peanuts, soy, wheat, tree nuts, fish and shellfish are the most common foods causing allergic reactions, but almost any food has the potential to trigger an allergy. Foods most likely to cause anaphylaxis are peanuts, tree nuts and shellfish.

Keep in mind that, if you are allergic to a particular food, you might be allergic to related foods. For example, a person allergic to walnuts may also be allergic to pecans and persons allergic to shrimp may not tolerate crab and lobster. Likewise, a person allergic to peanuts may not tolerate one or two other members of the legume family such as soy, peas or certain beans.

Clinical research of individuals with food allergy, however, has demonstrated that the overwhelming majority of patients with food allergy are only allergic to one or two different foods. Complete restriction of all foods in one botanical family based on an allergy to one of its members is rarely necessary. Discuss these issues with your Atlanta Allergy & Asthma physician.