Doxycycline
"I have suffered from Acne since I was around 9 years old (I am now nearly 23). I have started my 3rd month  on Doxcycline 100mg  once every morning. At the beginning of every month my face broke out with lots of whiteheads, this month has been the worse, slowly healing now but has left me with scaring. Hoping this will get better in the 3rd month as thats where people see most results. Whoever is on 50mg once a day for acne, you need to go back to your doctor/dermatoligst and up the dose, apparently 50mg won't do nothing for acne its a too lower dose. This is what my doctor told me. I have had no side effects as if yet."