Recent studies have shown that farm life reduces allergic rhinitis. Allergic rhinitis, more commonly known as hay fever, is the most common of the allergic disorders and it is also known to be a risk factor in asthma. Researchers in Sweden noted that allergic rhinitis is on the increase both in their country (where it affects 27% of the adult population) and elsewhere, so they set out to explore some of the environmental factors behind the problem.
Nearly 20,000 people aged 16-79 responded to a questionnaire about allergic symptoms and their lifestyle and life history. Those who had lived on a farm during the first five years of their life had protection from hay fever during the rest of their life, showing that farm life reduces allergic rhinitis. What is more, allergic rhinitis was more common among those living in an urban environment - something that has been noted in other studies.
So why are farms a protective environment against allergic rhinitis? It may be exposed to animal sheds, hay lofts or consumption of unpasteurized milk protects against allergic rhinitis. Another theory is that exposure to endotoxin, which is a compound made by certain bacteria, shifts the immune system so it is less likely to respond to common allergy and asthma triggers. But, to be honest, it is far from clear why growing up on a farm decreases your risk for developing allergies. However, the protective effect against allergic rhinitis of the farm/rural environment fits nicely with the other theme of this study, which is that the urban environment is a common allergy cause.
The Swedish researchers note that there is no difference between living in a mid-sized town to living in a large city such as Gothenburg when it comes to allergy risk. They speculate that there is a certain level of traffic-related air pollution found in urban environments that set the scene for allergy and is a large contributor to causing allergic rhinitis. Another theory is that reduced exposure to pollen in cities can make people less tolerant of it and therefore more likely to suffer from allergic rhinitis.
What is the take-home message of this allergic rhinitis study? Farming and rural communities are on the decline all over Europe. So opting to bring your family up on a farm, in the hope of avoiding allergies, is hardly a practical option. But what we can do is press strongly to make the urban environment healthier, which means taking measures to reduce traffic-based pollution. And there needs to be more research into the precise environmental factors in rural and urban environments which model the immune system away from, or towards, allergy.
Source: Erikkson J et al Growing up on a farm leads to lifelong protection against allergic rhinitis Allergy 2010; 65: 1397-1403