Acne
"I&#039;ve been on doxycycline for about 10 years at 100 mg, twice a day. It works great at clearing up my cystic acne that I get on my chin.  About six months ago I ended up with ulcers in my stomach and my Digestive Health Specialists thought it was the doxycycline causing it. Stop taking it for 4 weeks &amp; my acne was daily on my chin again. It&#039;s a great medicine, but hard on the stomach."