My 14-year old daughter had mild acne and begs taking doxycycline and tretinoin mid-November. Her acne is getting worse. Should she continue?

I think so. This may take 8 weeks to work. She may add topical benzoyl peroxide unless her physician thinks this is a poor idea. One fact that some people do not realize is that milk and antacids and iron deactivate tetracycline if taken near the same time. Best wishes.