One of the most common questions parents of my young patients ask me is “do you think this could be related to a food allergy?” There is often a certain amount of anxiety behind this statement, mostly because many of us associate food allergies in children with the stories we hear about life-threatening allergies to peanuts or shellfish.
The truth is that while many common childhood problems such as eczema, chronic ear and sinus infections, asthma and hyperactivity have an allergic component, most food allergies are not serious enough to cause these life-threatening reactions.
So what are food allergies? These are reactions that occur when a food protein or an inhaled particle triggers the production of antibodies in the immune system,
similar to what happens when we encounter a bacteria or virus. What happens next however is different. In classic allergies, these antibodies then bind to mast cells which line the mucus membranes of the mouth, nose, digestive tract and lungs. When this occurs, these cells release histamines and other chemicals which cause the typical symptoms of allergies; itching, runny nose and watery eyes, sneezing and hives. In rare cases, these reactions are severe enough to cause shortness of breath or closed off airways – the life-threatening symptoms known as anaphylaxis.
These types of reactions are controlled by a specific antibody known as IgE. They tend to happen rapidly after a food is ingested, usually within minutes although they can occur up to two hours after eating the offending food. The most common symptoms of IgE allergies are hives and swelling.
In some cases, pollen allergies in children can cause them to have reactions to certain foods that they wouldn’t react to normally. These tend to happen during high pollen allergy periods, such as late Spring or early Fall, and tend to appear in children with allergies to birch and ragweed pollens. Symptoms include itching and mild swelling of the lips and tongue after eating certain fresh, uncooked foods such as apples, cherries, carrots, potatoes, melons and banana. The symptoms usually stop within minutes after eating the food and while annoying, rarely progress to more severe symptoms. Interestingly, when these same foods are cooked, they often don’t provoke a response at all. We believe the reason this happens is because proteins of the foods are similar to the proteins of the pollens. When there are more pollens around, the immune system becomes less careful about what it considers an allergen. So then when it is exposed to a similar protein in a food, it reacts as if the food is an allergen. Cooking changes the structure of the food protein just enough to make it look different than the circulating pollen.
A third, much more common type of food allergy involves another immune system antibody, called IgG. These reactions can take hours or days to develop and involve a different process than IgE-type allergies. While antibodies are still produced, in this case they attach themselves to the allergens and form complexes that accumulate in places like the digestive tract, or the sinuses, or the capillaries of the hands and feet. These antigen-antibody complexes then give off chemical signals which can cause inflammation and contribute to many more chronic health problems.
Common symptoms that are associated with IgG allergies in infants and children are:
- dark circles under the eyes (called ‘allergic shiners’)
- nasal or throat congestion
- bloating, diarrhea and/or constipation
- colic, tantrums, crabbiness
- swelling of the hands or feet
- eczema, skin rashes or canker sores
- hyperactivity, poor focus, ‘brain fog’
The most common offending foods tend to be ones that are most prevalent in our diets: wheat (or gluten), dairy, eggs, soy and corn. The good news is that kids can often grow out of IgG allergies if the foods are removed from the diet for a few months and the inflammatory symptoms treated. The bad news is that IgG allergies, because they can take hours or days to occur after eating, are much more difficult to detect without either specific testing or a completely hypoallergenic diet. Both have their advantages and disadvantages, which I will discuss further in Part II.
For more information:
Bock K, Stauth C. Healing the New Childhood Epidemics: Autism, ADHD, Asthma and Allergies
– the Groundbreaking Program for the 4-A Disorders. New York: Ballentine Books, 2007.