Approximately 8% of US children have some kind of food allergy, researchers from Northwestern University Feinberg School of Medicine reported in the journal Pediatrics. 38.7% of those with a food allergy have a history of severe reactions, while 30.4% are allergic to several foods, the authors added.
Symptoms in a severe reaction may include wheezing and anaphylaxis, when the patient finds it hard to breath and has an abrupt drop in blood pressure.
The most common allergens for children were found to be peanuts, milk and shellfish.
Previous studies had estimated that 4% of US kids have some kind of food allergy.
Study leader, Ruchi Gupta, MD, MPH, wrote:
"The large, population-based nature of this study shows that pediatric food allergy is a significant and growing problem in our society. Based on our data, about 1 in every 13 children has a food allergy. What's more, nearly 2 out of every 5 affected children suffer from a severe food-allergy.
For these children, accidental ingestion of an allergenic food may lead to difficulty breathing, a sharp drop in blood pressure, and even death. Now that we understand just how far-reaching the problem of food allergy truly is, we can begin taking the necessary steps to keep these children safe."
Dr. Gupta and team evaluated data on nearly 40,000 American homes with children. Household members were asked several questions, including any past or present food allergies among children, when the allergy started, how it was diagnoses.
Dr. Gupta said:
"What makes this study so unique is not only the large number of households surveyed, but the amount of data collected for children with a reported food allergy. With this data we are able to differentiate between perceived and convincing food allergies, understand racial and economic differences in food allergy, and understand trends in food allergy diagnosis and testing. For example, Asian and Black children were more likely to have a convincing history of food allergy, but were less likely to receive a formal diagnosis when compared with White children."
The researchers hope their study will build awareness of the prevalence of food allergies, resulting in an overall improvement in the quality of life for children and their parents or caretakers.
Older children are more likely to have severe symptoms. The researchers believe this is because older children are supervised less intensively by their parents - a child of 14 is more likely to walk down the street and buy something containing, say peanuts, than a 4-year old who is next to a parent or adult most of the time. Peer pressure may encourage a 14-year-old to eat like the others in order to fit in.
The researchers also found that food allergy rates among Asian and African-American children are higher than in Caucasian kids. However, white children are more likely to have their condition diagnosed by a physician.
Peanuts, generally the most common food allergen in most parts of the world, are members of the bean family. A significant number of young children with peanut allergies eventually outgrow them.
Approximately 1 in every 50 kids is allergic to eggs - the majority of them are no longer allergic by the time they are five years old. Allergy to the egg-white is much more common than to the yolk.
The authors concluded:
"Findings suggest that the prevalence and severity of childhood food allergy is greater than previously reported. Data suggest that disparities exist in the clinical diagnosis of disease."
This was a very large study and the researchers were not able to use clinical measures, such as blood tests or medical records to count allergy cases.
Because the study relied on reports by parents and caregivers, some experts say the findings may not be completely accurate.
Difference between a food allergy and food intoleranceAn allergy means the individual's immune system overreacts to a harmless substance - it is unable to distinguish between that substance and a pathogen; something that harms health, such as some bacteria or viruses.
Allergic reactions to foods vary. They usually occur soon after eating, either in the form of swelling (inflammation) in the mouth or throat, or as a skin rash. Allergic reactions from foods that affect the gastro-intestinal tract, causing nausea, vomiting, diarrhea or constipation are very rare.
Food intolerance does not involve the immune system - nothing in the body is attacking a protein in the food. Food intolerance may involve an inability to digest an ingredient, perhaps because a required enzyme is inactive or absent.
People with food intolerance can usually eat tiny amounts of that food and get away with it. This is not generally possible with a food allergy - even very small amounts will trigger an immune reaction.
"The Prevalence, Severity, and Distribution of Childhood Food Allergy in the United States"
Ruchi S. Gupta, MD, MPH, Elizabeth E. Springston, BA, Manoj R. Warrier, MDd, Bridget Smith, PhDf, Rajesh Kumar, MD, Jacqueline Pongracic, MD, Jane L. Holl, MD, MPH
Pediatrics June 20, 2011. doi: 10.1542/peds.2011-0204
Written by Christian Nordqvist