Seasonal allergies are the worst. Video by Gina Barton and Liz Scheltens Millions of Americans suffer from seasonal allergies. There isn’t a clear-cut answer as to why some people have them while others don’t but scientists do have one particular theory. The hygiene hypothesis is the idea that excessively sterile environments are contributing to the development of allergies, asthma, and other autoimmune illnesses. Kids in wealthy countries lack exposure to allergens and other germs that aid in developing a healthy and functioning immune system. While the hygiene hypothesis isn’t the definitive answer to seasonal allergies, it is a starting point. Read more on seasonal allergies and the hygiene hypothesis: http://www.vox.com/2014/4/16/5616568/how-seasonal-allergies-work-and-why-you-get-them http://www.vox.com/2014/6/25/5837892/is-being-too-clean-making-us-sick Subscribe to our channel! http://goo.gl/0bsAjO Vox.com is a news website that helps you cut through the noise and understand what's really driving the events in the headlines. Check out http://www.vox.com to get up to speed on everything from Kurdistan to the Kim Kardashian app. Check out our full video catalog: http://goo.gl/IZONyE Follow Vox on Twitter: http://goo.gl/XFrZ5H Or on Facebook: http://goo.gl/U2g06o