text: what are the side effects of doxycycline? i have been taking doxycycline for acne for a few months, and i was wondering if this is bad for my health. this list is not a complete list of side effects reported with doxycycline. your health care provider can discuss with you a more complete list of side effects.  some possible uncommon but serious side effects of doxycycline include:      * a life-threatening allergic reaction (symptoms are trouble breathing; closing of the throat; swelling of the lips, tongue, or face; hives)      * blood problems (symptoms are unusual bleeding or bruising)      * liver damage (symptoms are yellowing of the skin or eyes, dark urine, nausea ,vomiting, loss of appetite, abdominal pain)      * irritation of the esophagus  other more common, but less serious, side effects include:      * nausea, vomiting, diarrhea      * increased sensitivity of the skin to sunlight      * vaginal yeast infection