Food allergies

About 25 percent of adults believe that they either have had a food allergy or know someone who does.  However, the frequency of a true food allergy in the general population is only about 4 percent in adults and 5 percent in children.

Food allergies will most commonly develop in children less than six years old.  A smaller percentage of people will develop an allergy later in life.  There is probably an inherited component to getting a food allergy since those who get it often have a family history of allergies.  However, environmental influences also play a role.  These would include exposures to certain types of foods and possibly infections or other alterations in the body’s immune system.  Infants and toddlers who are fed solid foods too early may also be at risk for developing a food allergy due to their immature digestive systems.  

The most common foods that cause allergies in children include: cow’s milk, egg, peanut, tree nuts, fish, shellfish, soybean and wheat.  These foods account for about 90 percent of all food allergies.  

In adults, the most common foods causing allergies are peanuts, nuts, fish and shellfish.  Allergy to peanuts affects about 0.6 percent of the U.S. population.  Often it is severe.  Additionally, a reaction to one nut may give an individual a reaction to other nuts (cross-reactivity).

What happens in the body with food allergy is that the person’s immune system mistakes a certain food as a harmful substance.  The body’s defenses make antibodies to that food.  Each time it’s eaten, the body reacts by producing inflammatory chemicals that cause the allergic reaction.  

Nine out of ten times the symptoms of food allergy will be seen in the skin.  Hives is the most common symptom.  Hives (urticaria) are raised, red welts on the skin that itch.  Other symptoms can include nasal congestion; itching ears, mouth or throat; swelling of the face and tongue; cough; trouble breathing; and generalized itching.  

A more severe reaction can occur (called anaphylaxis), wherein the individual experiences potentially life-threatening symptoms.  These include tongue and throat swelling, wheezing, difficulty breathing and shock.  This is a medical emergency and must be treated quickly, usually with medications such as adrenaline (epinephrine).  Milder allergic reactions, like hives, can be treated with antihistamines such as benadryl.  

In general, the best strategy when faced with a food allergy is strict avoidance of the offending food.  This means you have to be a vigilant label reader to identify potential problem foods.  Some foods can contain milk products, but it may not be obvious on the label.  For example, casein is milk-based and is included in some nondairy products.  Food manufacturers are required to indicate all major allergens on their labeling.  Another piece of good news is that research shows about 80 to 85 percent of children with cow’s milk and egg allergy will “outgrow” the reaction by age 10.          

The content in this column is for informational purposes only.  Consult your physician for appropriate individual treatment.  Dr. Reynolds practices Family Medicine in Chesterfield, 425-7771.

Comments

Food Allergy and intro of solid foods

This is OLD theory: "Infants and toddlers who are fed solid foods too early may also be at risk for developing a food allergy due to their immature digestive systems. " New scientific studies are finding this idea might be what is CAUSING the increase in food allergies. See: Pediatrics. 2010 Jan;125(1):50-9. Epub 2009 Dec 7.
Age at the introduction of solid foods during the first year and allergic sensitization at age 5 years.

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