Doctors may soon have a new weapon against acne: a harmless virus living on our skin that naturally seeks out and kills the bacteria that cause pimples.

Scientists in the US looked at two microbes: Propionibacterium acnes, a bacterium thriving in our pores that can trigger acne; and P. acnes phages, a family of viruses that live on human skin. The viruses are harmless to humans, but programmed to infect and kill the aforementioned P. acnes bacteria.

When P. acnes bacteria aggravate the immune system, it causes the swollen, red bumps associated with acne.

Most effective treatments work by reducing the number of P. acnes bacteria on the skin.

"We know that sex hormones, facial oil and the immune system play a role in causing acne, however, a lot of research implicates P. acnes as an important trigger," explained researcher Laura Marinelli, a UCLA postdoctoral researcher in Modlin's laboratory. "Sometimes they set off an inflammatory response that contributes to the development of acne."

Using over-the-counter pore cleansing strips from the drugstore, the researchers lifted acne bacteria and the P. acnes viruses from the noses of both pimply and clear-skinned volunteers.

When the team sequenced the bacteriophages' genomes, they discovered that the viruses possess multiple features - such as small size, limited diversity and the broad ability to kill their hosts - that make them ideal candidates for the development of a new anti-acne therapy.

"Our findings provide valuable insights into acne and the bacterium that causes it," said Graham Hatfull, a professor of biological sciences at the University of Pittsburgh and a Howard Hughes Medical Institute researche, who also worked on the study.

"The lack of genetic diversity among the phages that attack the acne bacterium implies that viral-based strategies may help control this distressing skin disorder."

"Phages are programmed to target and kill specific bacteria, so P. acnes phages will attack only P. acnes bacteria, but not others like E. coli," added Marinelli. "This trait suggests that they offer strong potential for targeted therapeutic use."

Scientists know little about what causes acne and have made narrow progress in developing new strategies for treating it. Dermatologists' arsenal of anti-acne tools - benzoyl peroxide, antibiotics and Accutane - hasn't expanded in decades.

Antibiotics are so widely used that many acne strains have developed resistance, and drugs like Accutane, while effective, can produce side effects.

Acne can dramatically disfigure people and undermine their self-esteem, especially in teens.

The research team plans to isolate the active protein from the P. acnes virus and test whether it is as effective as the whole virus in killing acne bacteria. If laboratory testing proves successful, the researchers will study the compound's safety and effectiveness in combating acne in people.

The study was published in the American Society for Microbiology's mBio journal.