A friend of mine has an allergy to poultry, of all things. Never can he partake in the joys of fried chicken, nearly all restaurant-produced soup (even claimed vegan soup is risky), most of Thanksgiving, or delightful Chicken in a Biskit crackers. It's a bummer, particuarly the never being able to eat at a restaurant without worrying about some chicken touching something somewhere and suddenly it's Benadryl time. Allergies like this are becoming more and more common–up 18 percent between 1997 and 2007–and a new study out in Annals of Allergy, Asthma and Immunology is claiming a connection between common pesticides and the food allergy surge.
There's currently 15 million Americans that have some kind of food allergy: poultry, peanuts, wheat, soy, dairy. Whatever. Some are deadly, some debilitating, some just give you a terrible rash. It's enough to make a pretty severe mark on the health care system and food industry. A study released this year said food allergies cost the health care system around a half billion dollars a year, which seems awfully low.
The individual costs to families are much more dire–figure the price of medications, specialty food markups, and, especially, that a great deal of allergy-related treatment happens via the emergency room. Is it a public health care black hole like diabetes yet? Not even close–diabetes costs around $116 billion a year–but the prognosis isn't good. A correlation between pesticide use and that rate of increase could be huge, both politically and real-world.
The specific culprit being examined here is 2,4-dichlorophenol. This metabolite is a byproduct of the chlorinating process used to treat household water, as well as being a chemical offspring of chlorophenoxyacetic acid, a pesticide used in agriculture. What 2,4-dichlorophenol does is sanitize things, kill off microbes both good and bad. As a result, we're less exposed to the good or at least neutral kind of microbes, and, thus, we have less infections. Western life is very hygenic, and this has been credited as a culprit in a lot of things, like superbacteria.
In this case, the theory goes that as we shut our bodies off to their environment, they become less adept at dealing with things in that environment. And food. So the task of the experiment in question was find a correlation between individuals testing positive for dichlorophenol in their urine, and those with food allergies. Using the National Health and Nutrition survey for 2005 to 2006–a massive meta-survey tracking the health and nutrition of some 10,348 people for a variety of purposes–the researchers came up with 2,011 individuals testing positive for dichlorophenol.
After controlling for a whole bunch of complicating factors–"Age, sex, race/ethnicity, vitamin D levels, pesticide use at home, creatinine level, the presence of asthma and hay fever, and residence of the participants"–found 411 participants with food allergies. Individuals without food allergies served as the analysis' control group. So 20 percent of the dichlorophenol-positive group had food allergies, which is quite a bit higher than the estimated 4 percent of adults in the general US population with food allergies, and this looks to be a noble effort at accurate representative sampling of said population.
A serious limitation noted in the paper is that their study includes mostly adults, whereas the actual distribution of food allergies favors kids heavily (8 percent to the adult pop's 4 percent). This is also simply an association framed by a general theory of sterility and disease. It might be interesting to see how this would do with a population selected uniquely for this purpose (as opposed to the meta-study dataset) and unique lab controls.
Researchers don't know for sure if its the sterilization effects of the dichlorophenol causing the allergies; that mechanism isn't well understood, and it'll be difficult to get much of a bead on it given that we're dealing with two very large and complex systems (the immune system and microbal populations.) It could well be that it's something more direct between dichlorophenol and the immune system, with the prior triggering the later to behave funny.
In other words, it might not have anything to do with Western culture and its hygeine obsession. At the very least, this study is reason enough to look further. Though this study is being hyped to all hell as you read this, usually that's all Very Big Deal mainstream science news actually is–a suggestion.