Sunshine is good for your Futon bedding and you!
We always encourage people to hang out in the sun or at least air their bedding regularly. It’s something that most people don’t do and this is not a good approach to an item you use for 8 hours per day. We discuss this in our video #4 on the main page, Caring For your Futon
Even in 1918 they worked out the the benefit of being outside in the sun
Richard has posted a great article on Medium about this