Food allergy occurs when the immune system mistakenly attacks a food protein. The body creates proteins called antibodies (IgE) that bind to the protein of the particular food to which one is allergic. Ingestion of the offending food may trigger IgE to bind to that food protein and cause the sudden release of chemicals, including histamine, resulting in symptoms of an allergic reaction. The symptoms may be mild (rashes, hives, itching, swelling, etc.) or severe (trouble breathing, wheezing, loss of consciousness, etc.). A food allergy can be fatal.
Food Allergy is a growing concern, especially when it is a child who is affected. The prevalence is highest in the first 2 years of life with a peak of 6-8% in one year olds. The prevalence falls progressively with time to an average of 3% of the total population. Food allergy does occur in adults, but it is much less common than in children. Up to 1/3 of parents will report an adverse reaction to foods that are not true allergies. These can include a rash around the mouth from strawberries, tomato products, and citrus as well as lactose or milk intolerance.
In children, the most common food allergens are milk, egg, wheat, soy, peanuts and nuts. Adults who develop food allergies are more likely to be allergic to peanut, tree nut and seafood, especially shrimp. Children can also develop allergies to shellfish and fish, especially as we introduce foods earlier to their diets. The good news for most children with milk and egg allergy is that 70-80% of them will outgrow these allergies with time. Recent studies suggest that on average, half of children with milk and egg allergy will become tolerant by age 8 and 12 respectively. The news is not as good for peanut allergy. Only 20%, (usually infants who develop peanut allergy) will become tolerant with time. Very few adults who develop allergy to tree nuts, peanuts or seafood become tolerant.
What Happens to Food Allergies Over Time?
Food allergy is often an early indicator that other allergies may follow. Children with food allergy, especially to eggs, have a 50-90% chance of developing allergies and asthma as they get older. Of milk allergic children, 50% will have an allergy to other foods and 40% of children with peanut allergy will develop allergy to other nuts. One third of children with bad atopic dermatitis will have a food allergy trigger.
Symptoms of Food Allergy
Reactions to foods can vary. Symptoms include urticaria (hives), angioedema (swelling), throat clearing, wheezing, vomiting, cramping, diarrhea, hypotension (low blood pressure) and death. Of the reported cases of near fatal and fatal anaphylaxis to peanut, delay in the use of injectable epinephrine was the number one cause for the fatal outcome. It is critical that patients with food allergy carry injectable epinephrine and that they are taught in the allergist’s office how to use it correctly. Since delayed reactions can occur, patients who use their epinephrine should proceed to their local emergency room for observation.
The Importance of Diagnosing Food Allergy
The food that caused the reaction may not be obvious. Therefore, at Atlanta Allergy & Asthma Clinic, we use allergy skin testing and CAP RAST (blood tests) to evaluate patients.
Allergy skin testing is the most accurate and preferred method of evaluating allergies. These tests are safe, minimally invasive, and easily interpreted. Blood assays or RAST may present the clinician with diagnostic challenges. Studies have shown variability between different labs so that results can be difficult to interpret.
Blood tests also have decreased sensitivity compared to skin testing. Results from blood tests can often take a week or longer to be reported.
There are times when an oral food challenge is performed to confirm a specific food allergy diagnosis. It is very important for a patient suspecting a food allergy be treated by an expert in the field, such as the doctors at the Atlanta Allergy & Asthma Clinic.
The most important aspect of treatment is an accurate diagnosis of food allergy.
Unfortunately there is no cure for food allergy at this time. Strict avoidance of the allergy-causing food is the ONLY way to prevent a reaction. Every patient should read labels on packaged foods and ask friends and family what ingredients they have used. Do not eat foods from a buffet that you cannot identify and do not be shy in restaurants. Always make the chef aware of your specific allergies.
Always be prepared for accidental ingestion by carrying self-injectable epinephrine. Do not leave home without an epinephrine auto-injector!!! There are currently three forms of auto-injectable epinephrine: Epi-Pen, Adrenaclick and Twinject. Make sure you are trained and comfortable with how to use the one you have.
If the epinephrine is used, proceed to the nearest ER for observation. The benefits of epinephrine may only last 15-20 minutes, which means the reaction is likely to recur. Use this time to call 911 and go directly to the ER for evaluation and additional treatment.
Oral Food Allergy Syndrome
Many patients with pollen allergy specifically to trees and weeds experience mouth and throat itching when eating some fresh fruits and vegetables. For example, a patient who is allergic to tree pollen may experience mouth itching when eating apples. Patients with ragweed allergy may experience mouth itching from eating melons and bananas. The list of tree/weed and fruit/vegetable cross reactivity is long. It is important to tell your allergist if you experience any of these symptoms.
The Food Allergy & Anaphylaxis Network is an excellent source for information about food allergies. Visit their web site at www.foodallergy.org.