I had sexual assault when I was a child since 10 years and I think I contracted syphilis. The symptoms I have mouth ulcers ,vision and hearing impairment, headache ,lack of concentration and anal itching so I think to take (doxycymine) 100 mg 4 capsule per day for 28 days is it harmful to take it if I didn't have the disease because I can't go to a doctor or make medical analysis and is the quantity of doxycymine is correct. Finally thanks allot.