ASK DR. BAUGHAN                                             December 12, 1997

IS IT A FOOD ALLERGY?

“Food allergies” are common areas of frustration and misunderstanding between patients and various types of health care providers.  There are lots of opinions and beliefs, and a slowly growing body of science.  The December 10, 1997 issue of the Journal of the American Medical Association is entirely devoted to different topics in allergy and immunology, and one article, by Hugh Sampson, M.D., reviews our current understanding of food allergies.

The article begins by defining food allergy as the body’s production of antibodies to substances in foods that result in symptoms within hours or a couple of days.  Food intolerance is a term used for other types of physical reactions to foods.  Intolerances may include metabolic reactions to foods such as lactose intolerance (due to the body’s lack of an enzyme to digest lactose, the sugar in milk products) or it may include chemical reactions to molecules in foods, such as tyramine in aged cheese causing headaches or high blood pressure.

Up to 25% of people think they have food allergies, but many have some intolerance, but not true allergy.  Careful studies indicate the true prevalence may be closer to 2 to 6%.  Part of the confusion about food allergies is that the similar molecules that may cause antibody reactions may be from foods that do not seem similar.  For example, there can be cross-reactions between celery, apple, kiwi and mugwort pollen.

The symptoms that most clearly can relate to allergic reactions include rashes, itchy eyes, congestion, facial or oral swelling, asthma and other breathing problems or anaphylaxis.  More difficult to assess are abdominal symptoms ranging from pain and diarrhea (more likely) to aching and gas (less likely).  Even more vague are fatigue, concentration or behavioral problems.

The most common foods implicated in allergies are eggs, milk, peanuts, soy, fish, nuts, and wheat.  People with eczema and other environmental allergies are more likely to have food allergies as well.  If babies are started on solid foods before 4 months of age, they are more likely to show food allergies.  Most physicians recommend avoiding cow’s milk and eggs until children are one year of age.

To accurately diagnose a food allergy requires considerable effort by patient and family.  A careful diary of everything a person eats and what symptoms they experience is an important first step, not just an impression of symptoms from the past.  Then suspected foods must be eliminated from the diet.  This often requires careful label reading by parents.  It also strains practical limits, given the way kids swap foods in school lunches or snacks at the convenience store or a friend’s house.  Negative skin or blood tests can be reassuring that someone does not have an allergy, but a positive test has limited value.  About 60% of positive tests do not reflect symptomatic reactions to foods.  After avoiding a suspect food for 10 to 14 days, the ideal test is to have powdered extracts of the food ingested in capsules.  But the extracts need to be compared to placebo capsules when neither the patient nor the physician knows which is the “real food capsule.”  Only the pharmacist knows for sure!  That takes a lot of careful planning.

Finally, treatment is limited.  Anaphylactic reactions can be treated like severe reactions to bee-stings, with epinephrine injections (Epi-Pen, Ana Kit, etc.).  Other medications often cause as many side effects as benefits.  So the treatment is to persist in eliminating the food from the diet, which takes a long term discipline and attention.  Fortunately, 85% of infants outgrow their food allergies by age 3, and one-third of older children and adults lose their allergic reactions after avoiding the allergen for 1-2 years.  For further information, contact the Food Allergy Network in Fairfax, Virginia at 1-800-929-4040.