"i&#039;ve been on doxycycline (100 mg daily for three months) twice, a year apart. the first time cleared my skin up beautifully. i had horrible cystic acne with new pimples popping up every day before i went to my dermatologist. i started clearing up within the first month. a year later, i started to break out again so i went back on it and my skin is back to being clear. i definitely recommend taking it with food, though. i got really bad heartburn for a week because i took this pill without eating."