"i had severe acne as a teenager and doxycycline did not have an effect. i ended up taking roaccutane which eventually left me with clear skin for 8 years. however, the last 9 months i have had a reoccurrence of moderate acne and was prescribed doxycycline. i was convinced it would have no effect again but within 3 days i saw an improvement. now after 2 weeks i have had no new spots. the first few days it made me feel really nauseous but more bearable if i take it with a meal and lots of water."