12 January - 20 June 2016

Study finds increase in food allergy not related to food sensitisation over time

ver the past few decades the prevalence of food allergy appears to have increased. This increase has caused researchers to investigate cause, such as timing of food introduction, and changes in diet and nutrition. A study published in The Journal of Allergy and Clinical Immunology by Keet et al. has investigated whether sensitisation to common food allergies increased in children from 1988-1994 to 2005-2006 and whether these trends differed by race and/or ethnicity.

Over the past few decades the prevalence of food allergy appears to have increased.  This increase has caused researchers to investigate cause, such as timing of food introduction, and changes in diet and nutrition.  A study published in The Journal of Allergy and Clinical Immunology by Keet et al. has investigated whether sensitisation to common food allergies increased in children from 1988-1994 to 2005-2006 and whether these trends differed by race and/or ethnicity.  

The scientists analysed stored blood samples which were collected from 7896 children aged between 6 -19 years who were involved in NHANES (4999 from NHANES III and 2901 from NHANES 2005-2006), cross sectional studies conducted by the National Center for Health Statistics of the Centers for Disease Control.  The blood samples were analysed for presence of food-specific immunoglobulin E (IgE - a blood marker associated with food allergy) for cow’s milk, hen’s egg white, peanut and shrimp.  Overall sensitisation was defined as food-specific IgE ≥ 0.35 kU/L for all foods, moderate-level sensitisation as food-specific IgE ≥ 2 kU/L for all food and high level sensitisation as food-specific IgE at or above values that previously have been considered 95% predictive probability cutoff (15 kU/L for milk, 7 kU/L for egg, and 14 kU/L for peanut).  The scientists note there currently is no cutoff for shrimp, so chose a value of 5 kU/L to define high sensitisation.  Using self-reports the team recorded race and/or ethnicity of the participants. 

After carrying out numerous statistical methods, Keet et al. found overall 24% of children were sensitised to milk, egg, peanut or shrimp in NHANES III and 22% of children were sensitised in NHANES 2005-2006.  There was no change in moderate-level food-specific sensitisation to any food.  The percentage of those with high-level food sensitisation decreased from 2.8% to 1.5%.  The only food which was found to have a significant change in prevalence was shrimp which was found to have a significant decrease in sensitisation for overall and high level sensitisation.   The scientists also examined age-specific trends for 6-9, 10-15 and 16-19 year olds.  In 16-19 year olds, there was a significant increase in high-level sensitisation to the combination milk, egg or peanut which the scientists report was due to an increase in high-level peanut sensitisation. 

In both surveys non-Hispanic black children had higher levels of sensitisation to milk, egg, peanut and shrimp than Mexican American and non-Hispanic white children. There was an increased prevalence of moderate and high-level sensitisation to the combination milk, egg and peanut among non-Hispanic black children but not in other groups, which the scientists state was largely due to an increase in moderate to high level sensitisation to peanut.

Keet et al. states that “these findings are contrary to our hypothesis that sensitisation to common food allergens increased in recent years and stand in contrast with a body of literature showing the increased health utilisation for its manifestations.” The study reports that the major shrimp allergen, tropomysin, is cross-reactive with cockroach, dust mite and nematodes, and it could be these cross-reactive allergens that could account for the shrimp findings.  More research is therefore necessary into this area. The team suggest that one possible explanation for the results, is that parents, patients and physicians are simply more aware of food allergies today than they were a few decades ago. Alternatively they state scientists know that although food-specific IgE antibodies are essential for the kind of food allergy that leads to anaphylaxis, many people with IgE antibodies to foods can eat those foods without problems. "These results raise the question of whether something has changed in the relationship between food-specific IgE and clinical food allergy over the past few decades.”

RSSL are industry experts in allergens, and provide a comprehensive range of testing, training and food allergen consultancy services to help you control and manage allergens within manufacturing and retailing.  For more information please contact Customer Services on +44 (0) 118 918 4076 or email enquiries@rssl.com  Don’t forget to join our Allergens in a Nutshell LinkedIn group.  

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