Try Ultrathon II by 3M its about 37% but uses a proprietary slow release formulatuion that keeps me bite free all day. Another application late afternoon and I'm good to go for the night. I react similarly to shuffles, badly, so when I find something that really works I'm pretty happy.

If you can get Aeroguard from Australia it's a wonder product as well that uses pyrethrins(sp?).