Acne medicines can be a pain in the throat.

Adolescents and young adults who receive antibiotics for acne are more than twice as likely during the year following treatment to develop an upper respiratory infection serious enough to warrant a visit to the doctor, according to a new analysis of health statistics.

Using a database of patients in Britain, scientists at the University of Pennsylvania School of Medicine in Philadelphia identified 118,496 people, average age 21, who were treated for acne. About three-fourths had received an oral or a topical antibiotic, or both, for more than 6 weeks. The others didn't get any antibiotic.

The researchers then noted how many people in each group were diagnosed with an upper respiratory infection marked by a severe sore throat during the following year. Nearly 19 percent of those getting antibiotics developed such an infection, whereas only 9 percent of those not given antibiotics did, the scientists report in the September Archives of Dermatology.

Prolonged exposure to antibiotics can wipe out some of the beneficial bacteria, or flora, in a person's throat, says study coauthor David J. Margolis, a physician and epidemiologist at Pennsylvania. "Altering somebody's flora might make them more susceptible to getting viral or bacterial infections," he says.--N.S.