A new study has revealed that a total of 7.5 million Americans, or 2.5 percent of the population, are currently suffering from a diagnosable food allergy to at least one food.
The study, which is thought to be the largest of its kind so far conducted, found young black children who also suffer from asthma appear to be the group most at risk. The research was a collaborative effort by investigators at institutions including Johns Hopkins Children's Center and the National Institutes of Health (NIH).
The study involved 8200 participants from age 1 to 60+ who gave blood samples and were interviewed by researchers. The investigators used the data collected to determine the prevalence of four food allergies and also to look at the association between food allergies and asthma, eczema and hay fever, known collectively as atopic illness. The findings are published in the Journal of Allergy and Clinical Immunology.
The researchers say the use of blood concentrations of IgE antibodies as an indicator of actual allergic disease makies this study the first of its kind to use that standard in thousands of participants. Indeed, only people with levels high enough to suggest clinical disease were classified as allergic. This is in contrast to other studies of this size which have looked at theoretical risk rather than the presence of actual allergies.
Senior investigator Darryl Zeldin, M.D., acting clinical director at the National Institute of Environmental Health Sciences (NIEHS) said "This study is comprehensive in its scope and is the first to use specific blood serum levels and look at food allergies across the whole life spectrum."
Overall, 2.5 percent of study participants had clinically significant blood levels of IgE antibodies to at least one of the foods tested. The most common allergy was to peanuts, with 1.5 percent of people testing positive. This was followed by shrimp/prawns (1 percent), eggs (0.4 percent) and milk (0.2 percent). The results also revealed that 1.3 percent of participants were allergic to more than one of these foods. Food allergies were also found to be most common in children 5 years old or younger, with 4.2 percent of them testing highly positive for one, followed by those between ages 6 and 19 (3.8 percent).
Additional findings revealed children under the age of 5 were more than twice as likely as young adults older than 20 to have a food allergy and black people were three times as likely as white people to have one, while men were nearly 1.9 times more likely than women to be affected.
Food allergies were more common in those with asthma. Those with asthma had nearly four times the risk of having a food allergy than those without it. Overall, people with food allergies were nearly seven times more likely than those without them to have required ER treatment for their asthma in the 12 months leading up to the study.
"Our findings confirm a long-suspected interplay between food allergies and asthma, and that people with one of the conditions are at higher risk for the other," says investigator Robert Wood, M.D., director of Allergy and Immunology at Hopkins Children's.
The strong association between food allergies and asthma did not appear to hold for hay fever and eczema. While people with food allergies were somewhat more likely to be diagnosed with hay fever, the link between the two was not particularly strong, and they did not appear to have higher risk for eczema, the investigators found.
Source: Liu AH, Jaramillo R, Sicherer SH, Wood RA, Bock SA, Burks AW, Massing M, Cohn RD, Zeldin DC (2010) National prevalence and risk factors for food allergy and relationship to asthma: Results from the National Health and Nutrition Examination Survey 2005-2006 Journal of Allergy and Clinical Immunology 126(4):798-806