When glands become clogged, a bacterium known as propioni multiplies quickly, leading to acne.
Acne has long been a teenage rite of passage. The eighth grade photo is supposed to show a few pimples, or at least the cakey makeup used to cover them up.
"I guess it's like braces," says Andrea Read. "You know, everybody has it."
But by the time young women reach high school, it's a different story, Read points out. Lots of her peers turned first to the common over-the-counter ointments such as Clearasil or Oxy pads.
"But as you get older, and you see the girls who had acne and suddenly it's disappeared. And you're like, 'What did you do?' They went to the dermatologist, and so I think people are just going more and more because they see it works on their peers."
Dermatologists prescribe antibiotics, from tetracyclines to erythromycin. The drugs are incredibly effective at stamping out the bacteria in oil glands that cause pimples and inflammation.
When patients see how well the antibiotics work, they want to stick with the treatment," explains Lawrence Eichenfield, a dermatologist at Children's Hospital and Health Center in San Diego.
But the practice of long-term antibiotic use is coming under scrutiny, he says.
"Increasingly there's information that makes us think twice about routine use of antibiotics for acne," Eichenfield says.
Research suggests such use is contributing to antibiotic resistance. There's also some evidence that long-term use puts people at an increased risk of illness. In one study, University of Pennsylvania researchers tracked the rate of upper respiratory tract infections in a set of acne patients.
"People who used antibiotics for their acne -- as compared to people who had acne who weren't using antibiotics -- were about twice as likely to develop an upper respiratory tract infection within a year's period of time," says David Margolis, one of the study's authors.
The results are not proof that antibiotics caused the increased infections. But Margolis says there are several theories to explain the connection. One is that antibiotics change the bacteria flora at the back of the throat -- making people more vulnerable to infections. Another theory is that the antibiotics lead to a sort of system-wide change in the body.
"There's a belief that some of these antibiotics may actually alter your immune system," says Margolis, "and this slight alteration could be the reason that somebody develops the upper respiratory tract infections we saw."
Sorting this out will require much more research, says James Del Rosso, professor of dermatology at the University of Nevada.
"That study is far from being definitive in terms of telling us what we need to do," says Del Rosso, and whether antibiotic use can lead to immune system changes. The study and the body of evidence, however, on antibiotic resistance can be viewed as caution flags, says Del Rosso.
"It gives us a signal of something we're already aware of," he explains. "We know that it's best, in an ideal world, that patients are not on long-term antibiotic therapy. The reality is that patients are there for treatment, and part of the effective treatment that we have to date is giving them antibiotics. And so we're caught in the middle until we have some better, definitive ways to solve the problem."
What many dermatologists are trying for now is to reduce dosage. Patient Andrea Read has cut back substantially on the dose of erythromycin she takes for acne, from twice a day, to once a day, and now, every other day.
Her dermatologist, Sandra Read, who is also her mother, says the strategy seems to be working.
"We're finding that we can find and gain control and maintain control with lower dosing," notes Sandra Read. Lowering the dosage also reduces side effects, such as heartburn, yeast infections and sensitivity to the sun.
Every patient is different, says Read. Increasingly, she's trying out combination therapies using retinoids, such as Retin-A, and various formulations of over-the-counter benzoyl peroxides.
At the end of the day, says Read, every patient is judging their treatment based on what they see in the mirror.
"We have very high expectations in our patients about how they want to look," she says.
Clear skin is a mark of beauty. And scientists' concern over antibiotic resistance isn't likely to stop teens who are in search of it.