What's the answer to this? After a winter in socks and boots, the skin on the back of my Achilles gets instant blisters in any shoe or sandal without socks or tights. Please tell me there's some need trick I can use so that I don't have to wear plasters on my heels all summer? Something to rub on my foot to toughen the skin maybe? It drives me crazy every summer, surely I can't be the only one... Tia