Hi you need to folow up with these questions to your doctor but taking doxy can give you white tongue. not sure about the rash but syphilis rash is ammost always on the hands and feet also the most used medicine for this is penicillian.
Thank you very much for the answer. I meant white patches on the tongue that are present in oral syphilis, that look similar to geographical tongue. Also I didn't develop a rash on hands and feet even though I know it's typical sign, in my case it showed up on the neck, head and torso, plus swollen lymph glands. I can't consult my doctor for the next two weeks cause I'm away. So I'd be very thankful if someone had any idea, if Doxycycline wouldn't work at all...