"you dirty rat!"
Dirty rats healthier than clean ones: Study
Flee-ridden wild animals had fewer allergies and autoimmune diseases
Backs theory over-sanitation is to blame for some Western health issues
Jun. 17, 2006. 01:00 AM
JOSEPH HALL
STAFF REPORTER
Dirty rats have fewer allergies and fewer instances of diabetes than their lily-white cousins, a new study sponsored by the U.S. National Institutes of Health says.
And what's true in rodents â with gutter rats and field mice exhibiting far fewer allergies and autoimmune diseases than their super-hygienic laboratory counterparts â is likely true for humans as well, the study says.
Supporting the "let them eat dirt" theory of child rearing, the research suggests that an overemphasis on cleanliness can actually open rodent â and human â populations up to endemic, immune-based ailments, says Duke University scientist Bill Parker.
"In humans, we know that if you are very clean, or live in a very clean country, then you have a tendency to get both allergies and autoimmune diseases," says Parker, an assistant professor of experimental surgery at the North Carolina school.
But among Third World human populations, which can face daily onslaughts of parasites and infectious agents, the incidence of allergies and autoimmune diseases is negligible, Parker says.
"And that's exactly what's going on with these rats," he says.
Parker's research, conducted at Duke, provides a probable mechanism to explain the long-observed phenomenon that connects hygienic societies with increased allergies and autoimmune diseases.
In autoimmune diseases, like insulin-dependent diabetes, arthritis and lupus, the body attacks its own tissues.
Comparing his flee-ridden wild rats with their clean and medicated laboratory counterparts, Parker discovered that the former had far higher levels of the antibodies associated with allergies and autoimmune diseases.
And while these elevated levels might have been expected to increase the incidents of both ailments amongst the wild rodents, Parker says the antibodies were actually busy fighting off real-life parasites and germs.
"In the wild rats, something in the environment was preoccupying the allergic-type responses and the autoimmune-type response of the rodents," Parker says.
While the lab rats had far lower levels of the relevant antibodies, they also had few germs or parasites to preoccupy them. With no real dangers to fight off, the antibodies targeted inert substances, like pollen or the body's own tissues, for attack.
In other words, Parker says, the lab rats' immune systems become hypersensitive to environmental or bodily substances that would not bother their wild counterparts in the least.
"A good analogy might be the little old person who lives alone in their house, that has nothing else to worry about, will get upset by the least little thing," Parker says.
"But if you look at somebody who's really, really had a rough life, it's going to be like water off a duck's back when it comes to agitating them."
But Parker does not argue that Third World conditions are healthier than the relatively sanitary environments typical in the developed world.
"We don't want to substitute typhoid for the sniffles, there's no question about that," he says.
Nor, he says, is it likely a good idea to keep your kids dirty, or to let them eat mud.
"Then, of course, you take a chance that they'll get some kind of infection that causes (more) harm (than allergies)," Parker says.
Parker does say, however, that researchers are now working on medicinal products that could introduce benign parasites into the body to try and manipulate the immune system into its natural working condition.
"The long-term goal would be to give somebody a pill, maybe at birth," Parker says. "It wouldn't cause a disease, but it would stimulate the immune system enough to prevent allergies and autoimmune disease."
Such a technique is currently being tested with inflammatory bowel disease patients, where porcine pinworm eggs are introduced into the lining of the gut to fine-tune their faulty immune systems.
Between 30 and 40 per cent of Canadians suffer from hay fever â the country's most common allergy â a two- to three-fold increase in the last few decades.