Update: a research study performed by Abou-Jaoude and colleagues presented on November 16th at the American College of Allergy Asthma and Immunology examines the link between maternal “mouth cleaning” of infant pacifiers and allergy. They found that “parental pacifier sucking was linked with suppressed IgE levels” in infants. Lower IgE is related to reduced risk of allergic diseases, including atopy and asthma. This work builds on the study by Hesselmar and colleagues that I describe below. Read on:
A study by Hesselmar and colleagues in the journal Pediatrics suggested that hand washing dishes may possibly affect allergy risk in children. This observational study involved about 1000 Swedish children. Kids whose parents used an automatic dishwasher had an increased risk of developing allergy and asthma. Handwashing was associated with a decreased risk ( odds ratio 0.57; 95% CI: 0.37- 0.85), on par with other protective factors such as eating fermented foods and being breast fed. Hesselmar’s group previously published a study linking the method of pacifier cleaning with allergy in children. Kids whose parents licked a pacifier clean (mouth cleaning), instead of boiling or tap water cleaning, had fewer allergies. In that previous study, dishwashing of pacifiers was linked with higher allergy risk. Hesselmar’s recent study suggests that machine dishwashing in general may be risky in terms of allergy and asthma risk in children:
Of course, it remains to be seen if machine dishwashing actually has a causal relationship with allergy, or if it is linked with some other important factor. The authors speculated that hand dishwashing is associated with increased microbial exposure, which has been shown to be protective against allergic diseases. This has been called the hygiene hypothesis – see Weinstock and Elliott 2009 – and Brown et al. 2013 – an idea that has gathered substantial support and refinement as we learn about the role of the microbiome in shaping early immune development.
Perhaps the most important early microbial exposure is that established by breast milk. Katie Hinde has made this the focus area of her research – read http://science.sciencemag.org/content/348/6242/1427
Dr. Hinde was a keynote speaker at the recent Evolutionary Medicine meeting in Park City Utah. She was joined by Gloria Dominguez Bello who described the importance of birth mode in establishing a beneficial microbiota in children. Read Dr. Dominguez-Bello’s recent work on birth mode and Bifidobacteria here: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0205962
Much work indicates that early exposures are the most important in being able to modify the risk for autoimmune and inflammatory conditions. Remarkable work in humans links gut microbiota composition with the risk of developing Type 1 diabetes. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4587635/
It is less certain whether microbiome interventions can have a big impact on outcomes in adults. Given the burden of allergic and autoimmune diseases, it makes sense that we should be interested in preventing and treating established disease. This might be best accomplished with diet, and perhaps with probiotics. We will explore these possibilities in Week 2 of the UNM Ev Med Elective.
Emergency Physician, Educator, Researcher, interested in the microbiome, evolution, and medicine