Thursday, January 26, 2012

Want To Avoid Allergies? Keep Your Kids Poor and Dirty.

What is it with newspapers and their crazy (one might even say prejudiced) conclusions about food allergies?

The latest study "summary" I read was entitled "The Downside of a Good Education: Food Allergies." The article opens with the following shot over the bow:
"People from well-educated families are almost twice as likely to suffer from some dangerous food allergies as others — possibly because their bodies’ natural defences have been lowered by rigorous hygiene and infection control, suggests a new Canadian study."
Really? The article seems to be saying that those with less education are somehow dirtier than the rest of their brethren, and therefore better protected. Can that really be true? And is it really what this study said?

To find out, I looked up the original study, which has a much less incendiary title of "Demographic Predictors of Peanut, Tree Nut, Fish, Shellfish, and Sesame Allergy in Canada." What does the article actually say, you ask?
"Peanut, tree nut, and sesame allergy were more common in children, while fish and shellfish allergy were more common in adults. Tree nut and shellfish allergy were less common in males. Shellfish allergy was more common in urban settings. Higher household education was associated with increased likelihood of allergy to peanut, tree, fish, and sesame although it reached significance only for tree nut. All food allergies were less common in immigrants although large CIs preclude definitive conclusions except for shellfish." 
The study goes on to speculate as to why this might be the case. Some of the reasons given are those oft trotted out: more antibiotics, more hand washing, less overcrowding. You know - poor people being dirtier. However, the studies cited at the end of this paper give an intriguing peak at other identified risk factors:
  • Vitamin supplementation in exclusively formula-fed children. 1
  • Cutaneous (skin) sensitization. 2
  • Common epitopes from soy formula triggering peanut sensitization. 3
  • Fungus on walls at home and renovation/painting in the house during pregnancy. 4
A final study I've never forgotten is the markedly regional skew (to the northern states) in the number of Epi-Pen(r) prescriptions. As the paper's brief summary notes, this may be linked to Vitamin D deficiency.

So...besides overcrowding and dirt, how might these interesting tidbits tie together with parental (and specifically maternal) education level?
  • Better educated (and therefore presumably wealthier) parents can better afford vitamin supplements.
  • They may choose more expensive skin products for their children that contain sensitizing plant proteins.
  • They may try more expensive soy formula options if milk-based formula causes sensitivities.
  • They may paint and remodel more prior to their baby's birth (due to availability of money/home ownership).
  • They may be more likely to use sunscreen (potentially causing or exacerbating Vit. D deficiency).
Are any of these the smoking gun? We'll never know if researchers and news outlets stop at the cultural conclusion that poor people are simply dirtier.