The tetracycline group of antibiotics still remains the most successful oral treatment for acne. They are relatively free from side-effects apart from the occasional gastrointestinal upset or vaginal candidosis. Rarer side-effects include drug rashes, pigmentation with minocycline and a light-sensitive eruption with doxycycline. The incidence of light-sensitive rashes with doxycycline at a dose of 100 mg daily, is in the order of 3%. Acne does not always respond to conventional regimens of antibiotics and higher dosages may be required. We report a highly significant incidence of light-sensitive eruptions in patients receiving doxycycline at a daily dose of 150 mg or above.