I bought some Birkenstock sandals last year after realizing I need substantial arch support. While my knees, hips and ankles (all of which vex me on and off) have never felt better, I find that I'm still getting blisters. I bought them this time last year and wore them most of last summer, and with socks in the house though most of our Canadian winter. As soon as was feasible, I pulled off the socks and hoped for the best -- and promptly redeveloped the same blisters I'd had the previous year.
I get horizontal blisters along the ball of my foot, more or less where the seam between the upper and the foot bed meet. This is an area where I always develop callouses, and the blisters are not tender or particularly troublesome, and seem to be a permanent summer feature on my feet now.
The sore ones are along the arch of my foot, which is high. They come and go and are more like raw patches than blisters.
Any suggestions on how to prevent the blisters? I have resorted to socks, which defeats the purpose of sandals, but at least I get the support of the Birks that prevents the knee and ankle pain. I've packed an extensive blister kit and invested in Smartwool socks, but wondering if you clever folks have other suggestions.