Blisters occur from friction. Friction is an indication that the brace is not aligning properly with the ankle or the brace is new and just needs to be broken in. To reduce the friction between the brace and the ankle during the break-in period, try wearing two pairs of long athletic socks under the brace. If after the recommended break-in period the brace is still causing a blister, check to make sure you purchased the correct size brace and that you did not use shoe size to determine brace size.