Growing up on a farm seems to make individuals resistant to respiratory and allergen problems. This tendency was noted by European researchers, who were curious to discover if the same resilience occurred in the United States.

Amish farmers, who share ancestry with the Swiss, typically use farming methods from the 19th century. Of the Amish farm kids studied, 5 percent had asthma, compared to 6.8 percent of the Swiss. And while 25 percent of the Swiss farm kids had allergies, only 7 percent of the Amish did.

Researchers led by Dr. Mark Holbreich theorized that growing up on the farm exposes young people to microbes, pathogens and allergens at an early age, allowing the immune system to recognize them but not to overreact and produce allergic symptoms (Kerry Grens, "Amish Farm Kids Remarkably Immune to Allergies: Study," Reuters, May 4, 2012).