Could exposure to biodiversity keep the doctor away? If you live in a city, you will find out soon. This allergy season may be a whole lot worse for city-dwellers living in areas where they’re not exposed to many different species of plants and animals.
That’s what a new study, which was carried out in Finland, found. The scientists behind the study tried to figure out whether reduced human contact with nature and biodiversity influences the composition of skin bacteria and allergen sensitivity. The authors tested 118 teenagers for an inflammatory disorder called atopic sensitization, or a disposition toward allergies, and also noted whether the subjects lived on farms or near forests or in the city. They found that the teens living closer to nature had more diverse bacteria on their skin and lower allergen sensitivity than individuals living in areas with less environmental biodiversity, such as urban areas or near bodies of water.
To go deeper, the researchers took blood samples and compared the presence of a special kind of bug, called gammaproteobacteria, with levels of an anti-inflamatory marker, IL-10, in the subjects’ blood. The presence of one gammaproteobacterial genus, Acinetobacter, was strongly linked to higher levels of IL-10 in healthy individuals but not in the allergen-sensitive ones. This suggests that these microbes may help teach the immune system to ignore pesky allergens. Gammaproteobacteria are commonly found in soil and on plants, but the way that the bacteria affect human immune systems isn’t completely clear.
Scientists have long wondered if the contents of our human microbial environments could make us more susceptible to asthma, allergies, and other chronic disorders—something known as the "hygiene hypothesis." The hygiene hypothesis generally says that the increase in antibiotics, vaccines, and antibacterial products has wiped out our immune systems’ abilities to fight off infection, causing systems to go haywire when they come in contact with innocuous substances like pollen. In this study, the authors take it even further: Biodiversity deprivation could be linked to the global megatrend of rising allergies and autoimmune diseases.
Being a parent or child today can be alarming: From peanut-free plane rides to special schools that cater to asthma and allergies, there has been a sharp rise in chronic immune problems. A study found that kids in 2008 were more than three times as likely to be allergic to peanuts than kids a living decade earlier, with a similar jump happening in other food allergies. Similarly, the prevalence of hay fever in developed countries has increased about 100% in each of the last three decades. Perhaps the answer to part of society’s health woes is getting a little closer to nature—or at least preserving biodiversity for future generations. "These results raise fundamental questions about the consequences of biodiversity loss for both allergic conditions and public health in general," write the authors of the study.