Food allergies are under-recognised risk factors for asthma, suggests a new study from the US that also found greater allergy incidence in children, men and black people than other sectors of the population.
Food allergies are caused by an adverse immune response, usually to a food protein, when the immune system identifies a protein as harmful. Estimates of incidence vary, but in recent years the sector of the food industry catering to allergy-sufferers – the ‘free-from’ market, has developed rapidly.
The researchers set out to develop nationally representative estimate es of food allergy prevalence and to investigate associations with asthma, hay fever and eczema. Their findings are published in the Journal of Allergy and Clinical Immunology.
They looked at food-specific serum immunoglobulin antibody data from 8203 participants in the US National Health and Nutrition Examination Survey 2005-6 aged between 1 and 60 years and, covering peanuts, cow’s milk, egg white and shrimp. The IgE and age-based criteria were used to define the likelihood of food allergy, and self-reporting was used to evaluate demographic risk and associations with asthma and other condition.
The estimated prevalence of clinical food allergy was seen to be 2.5 per cent – 1.5 per cent for peanuts, 0.4 per cent for milk, 0.2 per cent for egg and 1 per cent for shrimp.
Those seen to have an increased risk of possible allergies were non-hispanic blacks (3 times as likely), males (twice as likely) and children (twice as likely).
Black male children were 4.4 times as likely to have food allergies.
People who had ever received an asthma diagnosis were twice as likely to have food allergies as those who had not, and allergy risk was seen to increase with asthma severity: People who had received emergency care for asthma in the last 12 months were 7 times more likely to have food allergies than non-asthma sufferers.
"Our study suggests that food allergies may be an important factor, and even an under-recognized trigger for severe asthma exacerbations," said National Jewish Health Associate Professor of Pediatrics Andrew Liu. "People with a food allergy and asthma should closely monitor both conditions and be aware that they might be related."
However the researchers could not determine if food allergies were the cause of the asthma or if both asthma and allergies were manifestations of the same problem.
The Journal of Allergy and Clinical Immunology, Volume 126, Issue 4 , Pages 798-806.e13, October 2010
“National prevalence and risk factors for food allergy and relationship to asthma: Results from the National Health and Nutrition Examination Survey 2005-2006”
Authors: Andrew Liu, Renee Jaramillo, Scott H. Sicherer, Robert A. Wood, Allan Bock, Wesley Burks, Mark Massing, Richard Cohn, Darryl Zeldin.