Food allergies are more common among people with asthma and may contribute to asthma attacks, according to one of the most comprehensive surveys of food allergies ever undertaken. National Jewish Health Associate Professor of Pediatrics Andrew H. Liu and his colleagues also report in the November 2010 Journal of Allergy and Clinical Immunology that food allergies are more prevalent among children, males and non-Hispanic blacks.
"Our study suggests that food allergies may be an important factor, and even an under-recognized trigger for severe asthma exacerbations," said Dr. Liu. "People with a food allergy and asthma should closely monitor both conditions and be aware that they might be related."
The researchers, funded by the National Institute of Environmental Health Sciences (NIEHS), analyzed data from 8,203 people, aged 1 to greater than 60, who completed the National Health and Nutrition Examination Survey in 2005-2006, and had their blood tested for antibodies to four specific foods: peanuts, milk, eggs and shrimp.
"This study is very comprehensive in its scope," said Darryl Zeldin, MD, acting clinical director at the NIEHS and senior author on the paper. "It is the first study to use specific blood serum levels and look at food allergies across the whole life spectrum, from young children aged 1 to 5, to adults 60 and older."
Depending on the IgE antibody levels found in participants blood, they were categorized as sensitized to one or more of the foods or not sensitized. The sensitized participants were subdivided into those with an unlikely (10-20 percent), possible (50 percent) and likely (greater than 95 percent) chance of having food allergies.
Likely food allergies were twice as common among participants who had ever received an asthma diagnosis as among those with no asthma diagnosis.
The odds of having food allergies grew with increasing severity of asthma. Those who currently have asthma were 3.8 times as likely to have food allergies as those who had previously been diagnosed with the disease but no longer had it. Those who had visited an emergency department for asthma in the past year were almost seven times as likely to have food allergies as those who had ever been diagnosed with asthma but not visited an emergency department. Overall, 15.8 percent of participants who had visited the emergency department for asthma had IgE levels indicating possible or likely food allergies.
Researchers could not determine if food allergies actually cause asthma attacks or if asthma and food allergies are both manifestations of a severe allergic profile. They speculated that food-allergic reactions might be triggered in some people with asthma only when combined with strenuous exercise.
Overall, the researchers estimate that 2.5 percent or 7.5 million Americans have food allergies. This estimate is lower than some estimates, but in line with many others. This study's analysis of actual IgE antibody levels to foods in a large nationally representative sample lent authority to the results. However, since the tests measure potential allergies to only four of the most commonly allergenic foods, the results may slightly underestimate overall prevalence of food allergies, wrote the authors.
Children ages 1 to 19 were twice as likely to have food allergies as the general population. Non-Hispanic blacks were three times as likely to have food allergies, and males were twice as likely to have food allergies. Black male children were 4.4 times as likely to have food allergies.
Peanut allergy was the most common food allergy, affecting 1.3 percent of the surveyed population. Contrary to milk and egg allergies, which peaked in children under 5, peanut allergies were highest among children ages 6 to 19 (2.7 percent).