• What is food allergy?
• How can I tell if my child has food allergy?
• How can you diagnose food allergy?
• How do you treat food allergy?
• Can I prevent food allergy?
• Will my child always have food allergies?
  

What is food allergy?

Food allergy is an abnormal immune response to certain food(s) that the body reacts to as harmful. Estimates of the prevalence of food allergies range from approximately 4% to 8% of children and 2% of adults.^1,2  Though reasons for this are poorly understood, the prevalence of food allergies and associated anaphylaxis appears to be on the rise. Risk factors associated with food allergy include: family history of asthma and allergies, genetic predisposition to allergic disease, elevated allergen-specific serum immunoglobulin levels (IgE concentrations), and being younger than 3 years of age. There are eight foods that account for 90% of all food-allergy reactions cow’s milk, egg, peanut, tree nuts (for example, walnuts, pecans, almonds, and cashews), fish, shellfish, soybeans, and wheat.^2,3,4  While 3.3 million Americans are allergic to peanuts or tree nuts, 6.9 million are allergic to seafood. Combined, food allergies cause 30,000 cases of anaphylaxis, 2,000 hospitalizations, and 150 deaths annually.²
 
How can I tell if my child has food allergy?

Foods can cause a variety of different reactions. A true allergic reaction occurs when a child’s immune system makes an abnormal response to a food that they have eaten. As part of this abnormal response the child makes white blood cells called T cells and a blood protein called an IgE antibody that react to the proteins in the food. This response can lead to several types of reactions. The most serious type is anaphylaxis, which is a whole body reaction. Within minutes of eating the food, the child has itching, hives, sometimes vomiting, and may develop swelling of the face and throat, wheezing and difficulty breathing, shock, and loss of consciousness. This reaction can result in death, especially in children with asthma. In some children food allergy can cause only vomiting, diarrhea, and even blood in the stool. It is very unusual for food allergy to only cause respiratory symptoms such as asthma. Food allergy, however, can be an important trigger of eczema. Up to 30% of children with eczema have a significant food allergy. Sometimes the eczema will not improve until the food is taken out of the diet. Food allergies do not cause behavioral syndromes such as attention deficit disorder of autism.
 
How can you diagnose food allergy?

Most physicians diagnose food allergy by patient history and allergy testing. Studies of food allergy show that food allergy symptoms occur within 2 hours of eating the food. In patients with eczema they develop itching and redness of the skin within 2 hours of eating the food. Allergy testing can be done with either prick puncture skin testing or a blood test called a RAST (Radioallergosorbent Test). Both tests measure whether or not the child has made an IgE antibody to a protein in the food. It is important to know that there can be false positive test results, i.e. the test is positive but the child is not really allergic to that food. For this reason we only test to foods suspected by the parent or child to have caused a reaction.
 
Sometimes we will do a food challenge in which we give the child small amounts of the food suspected to cause the reaction. If there has been a life-threatening reaction (anaphylaxis), this challenge is always done in the clinic under very controlled conditions. In a child with eczema we will often do an elimination diet. We recommend removing the food from the diet for several weeks. The parent then restarts the food and watches carefully to see if the child develops itching or redness of he skin within 2 hours of ingestion. These challenges should only be done after consulting a physician and under their supervision.
 
How do you treat food allergy?
 
Avoidance is currently the only means of treatment. There are several exciting new approaches to treating food allergy but these are experimental. Allergy shots should not be given for food allergy, as there is a high risk of a life-threatening reaction. In one research study a patient died from a reaction to an allergy shot for peanut allergy. For children who have had a life-threatening reaction an Epi-pen© should always be available. An Epi-pen© is a device that gives an injection of epinephrine into a muscle. Epinephrine is a hormone that can reverse the life-threatening reaction. If the Epi-pen© is used then the patient should be taken immediately to an emergency room. The epinephrine only lasts for about 30minutes and the reaction may recur when it wears off.
 
Can I prevent food allergy? 

There is evidence that avoidance of foods that frequently cause allergy may prevent food allergy in infants and young children. Infants at high risk for food allergy include those whose both parents have allergies or one parent and a sibling have allergy. The American Academy of Pediatrics recommends exclusive breast-feeding until 6 months of age. Cow’s milk should be avoided until 12 months of age, eggs until 24 months, and peanuts, tree nuts, and fish until 36 months.
 
Will my child always have food allergies?

The length of time a child may experience food allergies depends on the specific food. Many young children lose their allergy to cow’s milk and eggs by 4-5 years of age. On the other hand, peanut allergy is usually life long with only about 15% of people ever losing their reaction to peanuts.

Related Information: See Eosinophilic esophagitis (EE) 

References:

1. CDC. Allergic conditions among children: US, 2000-2005 (Source: NHIS) Available online at  http://209.217.72.34/HDAA/TableViewer/tableView.aspx?ReportId=205. Accessed September 17, 2007.
2. Report on the Expert Panel on Food Allergy Research, June 30 and July 1, 2003, National Institute of Allergy and Infectious Diseases, National Institutes of Health. http://www3.niaid.nih.gov/about/organization/dait/PDF/june30_2003.pdf [PDF 190K].
3. Sampson H. Food Allergy. Journal of Allergy and Clinical Immunology 2003; 111(2):540-547.
4. Sicherer SH, Muñoz-Furlong A, Murphy R, Wood RA, Sampson HA. Symposium: Pediatric Food Allergy. Pediatrics 2003; 111(6):1591-1594.
5. US Food and Drug Administration. Food Allergies: What you need to know. Available online at http://www.cfsan.fda.gov/~dms/ffalrgn.html. Accessed September 20, 2007.
6. National Institute of Allergy and Infectious Disease. Food Allergy: An overview. Bethesda, MD: July 2007. NIH Publication No. 07-5518.

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