Eczema in the first two years of life linked to common food allergies
Eczema in the first two years of life appears to be associated with common food allergies, according to results of a case control study published in the International Archives of Allergy and Immunology (May 2015; 166(3):199–207).
This study referred to as the SPAACE study (Surveying Prevalence of Food Allergy in All Canadian Environments) consisted of a cross-Canada random telephone survey that occurred between Sept. 2010 and Sept. 2011.
Participants included in the investigation were 480 individuals with either self-reported convincing symptoms or a physician’s diagnosis of an allergy to any of nine common food allergens to milk, egg, peanut, tree nut, shellfish, fish, wheat, soy, or sesame. A total of 4,950 healthy controls also completed the survey, the authors reported.
According to investigators, the questions in the survey asked about environmental factors including daycare attendance, pet ownership, whether the individual spent time living on a farm, as well as personal and family history of atopy including both eczema and asthma.
“We were especially interested in eczema in early life because all [recent] studies suggest that events in the environment that occur in early life are crucial to the development of food allergy and tolerance,” says study lead author Dr. Moshe Ben-Shoshan, assistant professor, Division of Pediatric Allergy and Clinical Immunology, Department of Pediatrics, McGill University Health Center in Montreal.
Data showed that for all of the included allergens, there was an increased risk of allergy associated with three factors: a personal history of eczema in the first two years of life, asthma, or hay fever (odds ratio (OR) 2.3, 95% CI 1.6–3.5; OR 2.8, 95% CI 2.2–3.6, OR 2.3, 95% CI 1.8–3.0 respectively); food allergy in parents or siblings (OR 3.7, 95% CI 2.5–5.6 for mother, OR 3.0, 95% CI 1.8–5.1 for father, and OR 3.1, 95% CI 2.2–4.2 for siblings), and high household income (top 20%, OR 1.5, 95% CI 1.2–2.0).
It is not surprising to find atopy and generalized eczema associated with food allergy, says Dr. Ben-Shoshan, “but the interesting part is that we showed that eczema in the first two years of life is crucial for the development of food allergy and is associated with higher risk of food allergy, especially peanut and tree nuts, but less likely to milk.”
This supports the dual allergen exposure hypothesis, he says. “So if you have early onset of eczema then you are more likely to be introduced to food allergens in an undesirable way—a way that will lead more to allergy rather than tolerance.”
Dual allergen exposure
The dual allergen exposure hypothesis was proposed by Dr. Gideon Lack in 2008 in a report published in The Journal of Allergy and Clinical Immunology (June 2008; 121(6):1331–1336).
“When you introduce something early in life in large amounts through the mouth, you are more likely to induce tolerance. But when the skin is impaired and the first introduction is through the impaired skin barrier, you do not have the same tolerance-inducing mechanism and you might induce allergy,” says Dr. Ben-Shoshan of the hypothesis.
Previous research published in The Journal of Allergy and Clinical Immunology (Jan. 2013; 131(1):135–143.e1–12) from U.K. investigators showed that in children at higher risk of food allergy—and children with eczema are at higher risk of developing food allergy—early introduction of peanut is better for inducing tolerance instead of allergy, says Dr. Ben-Shoshan.
“Our study supports that and extends it to most food allergens, except milk, because I think milk is introduced early in life even before eczema starts to appear,” he says. “[The findings] show that you probably need to protect the skin at the same time you introduce food through the mouth. I think it has practical implications.”
Eczema on the rise
The findings of the study are particularly important because other research has shown that the rate of eczema in the world is increasing, particularly in North America, says Dr. Ben-Shoshan.
“So the question is now why is eczema rising in prevalence?” Colder, drier environments are known to be associated with increased loss of moisture from the skin, he says.
Dr. Ben-Shoshan questions whether the increase in eczema prevalence could be related to environmental factors such as more people staying indoors being exposed to air-drying central heating and air-conditioning or immigrants having skin that is not used to the Canadian climate.
More research is needed, said Dr. Ben-Shoshan, who added that in the future he would like follow up this research with a study in twins to investigate how genetic factors interplay with environmental factors in the development of food allergy.
Dr. Ben-Shoshan would like to disclose that their study was supported by AllerGen and Health Canada.
Note: This article was published in the Oct./Nov. issue of The Chronicle of Skin & Allergy.