Growing up on a farm is linked to a lower risk of developing allergies as an adult, and stronger lungs in women, than growing up in either a rural or urban area, according to new research.

The findings, published online in the BMJ journal Thorax, are based on an analysis of the medical records of people in 14 countries — suggesting that common biological factors, rather than social or cultural ones, may have a role to play, say the researchers.

Experts believe the likely culprit is something known as the “hygiene hypothesis” — a theory that suggests early childhood exposure to a wide variety of potential allergens and microbes may offer some protective effect against allergies or somehow strengthen the immune system.

Past studies have suggested the sharp rise of asthma and allergies over the past few decades in urban and affluent areas may be partly explained by the hypothesis.

For the latest study, the researchers drew on the European Community Respiratory Health Survey II, which included more than 10,000 people aged 26 to 54 from 14 countries in Europe, Scandinavia, and Australia between 1998 and 2002.

Participants were asked where they lived before the age of 5 — on a farm; in a country village; in a small town or city suburb; or inner city.

The results showed that nearly two thirds of the study participants had lived in a rural village, small town, or city suburb before the age of 5. One in four had spent their early childhood in an inner city, and almost one in 10 grew up a farm.

Those who had spent time as children on a farm were 54 percent less likely to have asthma or hay fever and 57 percent less likely to have allergic nasal symptoms than those living in an inner city.

Farm kids were also less likely to have had a family history of allergies than the others, and were more likely to have had pets, older siblings, and to have shared a bedroom in their early childhood.

“The consistency of the findings across multi-country settings suggests that farming effects may be due to biological mechanisms rather than socio-cultural effects that would differ between countries,” the researchers concluded.