great! that's exactly the kind of info i needed. Thanks Mrs D

But no, i never had open sores on my fingers, just specific areas of skin on my fingertips about the size of a pea, which are hypersensitive. It was these areas that dried out and hardened during the first week of the doxy which lead me to think it was doing something. Unfortunately, they healed just as quickly and went back to being hypersensitive again :/