Understanding Food Allergies

What are food allergies?
A food allergy is an exaggerated response of the immune system against harmless proteins found in certain foods. Symptoms usually occur shortly after eating even a tiny amount of common allergy-causing foods such as milk, eggs, and peanuts. If a child has a food allergy it is important to determine the cause and avoid foods that trigger a reaction that can range from mild to severe or even life threatening. Teenagers and young adults with food allergies are at the highest risk of fatal food-induced anaphylaxis.

How Many People Have Food Allergies?
It is estimated that that up to 15 million Americans have food allergies, with one in every 13 children under age 18 affected. There are approximately 200,000 emergency department visits per year and 300,000 ambulatory-care incidents a year among children under the age of 18, and the economic cost of children's food allergies is estimated to be nearly $25 billion per year.

What Foods Cause Allergic Reactions?
Any food can cause a food allergy, but most food allergies are caused by the following:
• Cow's milk
• Eggs
• Peanuts
• Soy
• Wheat
• Nuts from trees (such as walnuts, pistachios, pecans, cashews)
• Fish (such as tuna, salmon, cod)
• Shellfish (such as shrimp, lobster)

Peanuts, nuts, and seafood are the most common causes of severe reactions. Allergies also occur to other foods such as meats, fruits, vegetables, grains, and seeds, such as sesame.

A recent study found that 8% of children under age 18 are allergic to at least one food. Previous studies estimated that proportion at about 4%. Peanut allergies were the most common, affecting 2% of children; milk was second most common and shellfish allergies third most common. Tree nuts, egg, finned fish, strawberry, wheat, and soy were also among the top nine food triggers.

The good news is that food allergies are often outgrown during early childhood. It is estimated that 80% to 90% of egg, milk, wheat, and soy allergies go away by age 5 years. Some allergies are more persistent. For example, only 1 in 5 young children will outgrow a peanut allergy and fewer will outgrow allergies to other nuts or seafood. A pediatrician or allergist can perform tests to track a child's food allergies to see if they are going away.

What are the Symptoms of a Food Allergic Reaction?
Signs and symptoms that a person may be having an allergic reaction include:
• tightness in the throat
• itchy eyes
• itchy skin
• skin rash (hives or eczema)
• swelling of lips or face
• hoarse voice
• wheezing
• cough
• nausea
• vomiting
• stomach pain
• diarrhea

Studies suggest that 40% of children with food allergies experience severe symptoms such as wheezing and, in the most severe cases anaphylaxis, a life threatening condition. Anaphylaxis is a medical emergency in which several of the symptoms of an allergic reaction occur suddenly and simultaneously with difficulty breathing and a sudden drop in blood pressure. Swelling of the throat and bronchospasm prevents breathing and swallowing, the heart rate rises and blood pressure drops suddenly. Immediate treatment with epinephrine (adrenalin) is needed. If a child has been prescribed an epinephrine auto injector, it should be with them at all times and used immediately at the first sign of an anaphylactic reaction. 911 should be called immediately. A second dose of epinephrine should always be on hand in case it is needed.

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Milk and Soy Allergies
Allergies to milk and soy are usually seen in infants and young children. Often, these symptoms are unlike the symptoms of other allergies, but, rather, may include the following:
• colic (fussy baby)
• blood in a child's stool
• poor growth

How are Food Allergies Diagnosed?
If a food allergy is suspected, an allergist will take a complete medical history and perform a physical exam. Because the history usually is the most important tool in diagnosing food allergy, a parent or child should be prepared with a complete list of foods the child had consumed before the reaction as well as the signs, symptoms, severity and length of the reaction.

Because many symptoms and illnesses could be wrongly blamed on food allergies, it is important for parents to know the usual symptoms to distinguish a true food allergy from other abnormal responses to food, such as the food intolerances that are far more common than food allergy. Food intolerance often causes abdominal pain or cramps or diarrhea. This can be caused by cow's milk products when a person is lactose intolerant, and by grains containing gluten, such as wheat, barley, and rye, when a person has celiac disease. Food poisoning from food contaminated with bacteria and viruses and food additives may also cause food intolerance. Other gastrointestinal diseases may cause abdominal symptoms that can resemble food allergies.

If a history alone cannot determine the diagnosis, it may be helpful to keep a dietary diary that provides a record of the contents of each meal and whether reactions occurred that are consistent with allergy.

The next diagnostic step that some doctors use is an elimination diet. If after the patient removes the food, the symptoms go away, the doctor almost always can make a diagnosis of food allergy. Only if the symptoms are not severe, the physician may ask the patient to resumes eating the food. If the symptoms return, the diagnosis is confirmed.

If the patient's history, dietary diary, or elimination diet suggests that a specific food allergy is likely, the doctor may use tests, such as skin scratch tests, blood tests, and a food challenge, which can more objectively confirm an allergic response to food. The oral food challenge is the gold standard and only definitive test to diagnose food allergy. It is typically done in the allergists office, and only if the risk of anaphylaxis is low.

Can Food Allergy Be Prevented Altogether?
The development of food allergies cannot be prevented, but can often be delayed in infants by: breastfeeding infants for the first 6 months, avoiding solid foods until an infant is 6 months of age or older, and avoiding cow's milk, wheat, eggs, peanuts, and fish during a child's first year.

Allergy shots for immunotherapy are given with the aim of desensitizing a patient to allergens without developing symptoms. Immunotherapy is effective in controlling symptoms of allergies related to hay fever, insect bites and indoor allergens, but it has not been proven to prevent allergic reactions to food.

What Is the Treatment for a Food Allergy?
There is no cure for food allergies and there is no medication to prevent food allergy. The only "treatment" is prevention, by avoiding foods that cause reactions. If a child has a food allergy, both parents and children need information about how to stay safe and healthy at home and in school.

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Dietary Avoidance
Avoiding the offending allergen in the diet is the primary and best treatment of food allergy. The FDA requires that the ingredients in a food that is sold be listed on its label. People with food allergies need to carefully read the lengthy, detailed lists of ingredients on the label for each food they consider eating. Doctors and allergy organizations also can help by providing lists of safe foods and unsafe foods.

Some people who are very sensitive may need to avoid foods just because they are made in the same factory that also makes their problem food. Many allergy-producing foods such as peanuts, eggs, and milk appear in foods that are not ordinarily associated with them. For example, peanuts are often used as protein supplements, eggs are found in some salad dressings, and milk is in bakery products. Eating out is often a challenge. When in restaurants, ask what goes into foods and avoid ordering foods that might contain ingredients to which you are allergic.

Treating an Anaphylactic Reaction
People with severe food allergies must be prepared to treat an anaphylactic reaction. They need an emergency plan to cope with accidentally eating the wrong food. The plan should spell out what to do, who to tell, and which medicines to take if you have a reaction. To protect themselves, people who have had anaphylactic reactions to a food should wear medical alert bracelets or necklaces stating that they have a food allergy and that they are subject to severe reactions. These individuals also always should carry a syringe of adrenaline (epinephrine [EpiPen]), obtained by prescription from their doctors, and be prepared to self-administer it if they think they are developing an allergic reaction. They then should immediately seek medical help by either calling the rescue squad or having themselves transported to an emergency room.

Treating Other Symptoms of Food Allergy
Several medications are available for treating the other symptoms of food allergy. For example, antihistamines can relieve gastrointestinal symptoms, hives, sneezing, and a runny nose. Bronchodilators can relieve the symptoms of asthma. These medications are taken after a person inadvertently has ingested a food to which he is allergic. They are not effective, however, in preventing an allergic reaction when taken prior to eating the food.

Food allergy is caused by immune reactions to foods, sometimes in individuals or families predisposed to allergies. When a food allergy is suspected, a medical evaluation to confirm the diagnosis of food allergy and the attainment of knowledge about allergies and how they are diagnosed and treated are important to proper management.

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Sources and Links

Information and portions of text used in this essay have been derived from the following sources:

A free book on food allergies can be downloaded at: www.kidswithfoodallergies.org
National Library of Medicine www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001820
American Academy of Allergy, Asthma, and Immunology www.aaaai.org/conditions-and-treatments/library/at-a-glance/food-allergy.aspx

National Institute of Allergy and Infectious Diseases www.niaid.nih.gov/topics/foodAllergy/understanding/Pages/default.aspx

JAMA Patient Page-Allergy, JAMA July 24/31, 2013 Volume 310,Number 4.





Food Allergy & Anaphylaxis Network. http://www.foodallergy.org/.
Sicherer, Scott H. "Food Allergies." Medscape.com. Mar. 17, 2011.

U.S. National Institute of Allergy and Infectious Diseases. "Food Allergy." May 3, 2010. http://www.niaid.nih.gov/topics/foodallergy/Pages/default.aspx.

.Young, E., M.D. Stoneham, A. Petruckevitch, J. Barton, and R. Rona. "A Population Study of Food Intolerance." Lancet 343.8906 May 7, 1994: 1127-1130.





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