Further into the cats-&-dogs story at the U of Cincinnati

Anyone with access to a computer has by now heard the news: "man's best friend protects against eczema in young children."

That's the short version, anyhow. I first noticed it on Twitter, and automatically retweeted, as did it seems half the Twitterverse. It's a nice short soundbite and I'm sure it played well on TV, too. (Wouldn't know--don't watch.)

This is a good introduction for me. I would like to explore the universe of eczema research, first in North America, and then beyond. I'm most familiar with the North American research sphere, having worked in it, and at the moment writing PR as part of the research-industrial complex. So I am happy to learn there is a group conducting research of this type at the University of Cincinnati. Maybe we can explore the group's work further.

There's definitely something up with cats and dogs and allergens. I know this from personal experience. I'm deathly allergic to cats. Certain species (I'm allowing for variation) in certain circumstances (like my late grandmother's apartment, which housed at least three felines of great hairiness and size, and which wasn't cleaned from approximately 1975 to 1994, when she passed away) give me instant and incredible fits of itching and sneezing. Dogs don't, although when they lick me, I get hives. I used to like cats, until I had a skin prick test that showed I had high reactivity, and ever since, they've seemed like the spawn of the devil.

So: cats and dogs. The results of the Cincinnati study are more subtle than might seem from a quick read of a mass-market website or newspaper. If you read the university's press release, or the actual paper, what the authors find is that if 4-year-old kids are allergic to dogs, their risk of developing eczema is 4 times higher than average if they did NOT have a dog in the home before they were one year old. If 4-year-olds are allergic to cats, they are 13 times more likely to have eczema than average if they DID have a cat in the home before they were one year old.

So you see the findings apply only to kids who are allergic to the pet in question. But this is interesting, because when you've become allergic to something, your immune system has had a fundamental reaction to some allergenic factor. Your B cells are producing antibodies to it. The inflammatory response is involved.

The authors are not immunologists, but they do refer to an earlier study that showed that "T cell lines of dog-allergic subjects produce high levels of interleukin-10 and interferon-gamma, cytokines associated with the induction of tolerance." The tolerance in question is to dog allergen. Not sure how being tolerant of dog allergen is related to being allergic to dogs. I'd ask the authors, but after the media blitz I don't think they'd have time for an anonymous blogger.

This paper certainly makes clear that I'm going to have to educate myself in statistics. When I'm reading about adjusting for confounding variables, I feel like I'm in one of those dreams where I forgot to wear my pants to math class.

There are other interesting factors in this paper that the media generally left out of their stories, and I'd like to discuss these in subsequent posts. Among them: genetic heritability and filaggrin mutations.