What Are Food Allergies?
A food allergy results when the immune system mistakenly targets a harmless food protein—an allergen—as a threat and attacks it. Unlike other types of food disorders, such as intolerances, food allergies are “IgE mediated.” This means that your immune system produces abnormally large amounts of an antibody called immunoglobulin E—IgE for short. IgE antibodies fight the “enemy” food allergens by releasing histamine and other chemicals, which trigger the 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 two years of life with a peak of 6–8 percent in one year olds. The prevalence falls progressively with time to an average of three percent of the total population. Food allergy does occur in adults, but it is much less common than in children. Up to one-third 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.
Although nearly any food is capable of causing an allergic reaction, eight foods account for 90 percent of all food-allergic reactions in the United States. These foods are: Peanut, Tree nut, Milk, Egg, Wheat, Soy, Fish and Shellfish.
In children, the most common food allergens are milk, egg, wheat, soy, peanuts and tree nuts. Adults who develop food allergies are more likely to be allergic to peanut, tree nut and seafood, especially shrimp; however, children can also develop allergies to shellfish and fish.
The good news for most children with milk and egg allergy is that 70–80 percent 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 eight and 12 respectively. The news is not as good for peanut allergy. Only 25 percent, (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.
Reactions to foods can vary. Symptoms include urticaria (hives), angioedema (swelling), throat clearing, wheezing, vomiting, cramping, diarrhea, hypotension (low blood pressure) and in some cases—death from anaphylaxis.
Anaphylaxis is a severe allergic reaction that occurs very rapidly. Food allergy is the most common cause of anaphylaxis, although several other allergens—insect stings, medications, or latex—are other potential triggers.
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. It is recommended that those with a food allergy carry two doses since delayed reactions can occur. If epinephrine is administered for a reaction, the patient should proceed to their local emergency room for observation.
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 percent of developing allergies and asthma, as they get older. Of milk allergic children, 50 percent will have an allergy to other foods and 40 percent of children with peanut allergy will develop allergy to other nuts. One-third of children with severe atopic dermatitis (eczema) will have a food allergy trigger.
The Importance of Diagnosing Food Allergy
The food that caused the reaction may not be obvious. Therefore, at Atlanta Allergy & Asthma, we often use more than one type of test to diagnose food allergy. Allergy skin prick testing, ImmunoCap (blood tests), and when appropriate, oral food allergy challenges are utilized to confirm a diagnosis. Additionally, we are now able to conduct component testing for peanut allergic patients to determine the risk of having a severe reaction.
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 ImmunoCap 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. This should be done in a medical facility by a board certified allergist who is specially trained in this procedure. It is very important that a patient suspecting a food allergy be treated by an expert in the field, such as an allergist at Atlanta Allergy & Asthma.
The most important aspect of treatment for food allergy is an accurate diagnosis.
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 several forms of auto-injectable epinephrine: Epi-Pen, AuviQ, and generic epinephrine (formally Adrenaclick). Make sure you and those close to 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 can reappear. 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.
An accurate diagnosis by a board certified allergist is the first step in living with food allergy, however we urge patients to connect with others that are dealing with the same challenges. These are excellent website and local family support groups that help families that are seeking information and advice. We have listed several below:
Food Allergy Research and Education (FARE) is an excellent source for information about food allergies. Visit their web site at www.foodallergy.org.