March 6 (HealthDay News) -- Laser therapy can safely and effectively treat mild to severe cases of acne, according to a small preliminary study of 18 people.

Fourteen of the participants were treated with a combination of photodynamic therapy (PDT) using a long-pulsed, pulsed-dye laser and a photosensitizer called topical 5-aminolevulinic acid (ALA). People received one to six treatments, depending on the severity of their acne, and continued to use topical medications during and after the study.

The four participants in the control group were treated either with conventional therapy (systemic or topical medications) or with laser energy but without ALA PDT.

Complete clearance of acne was achieved in all 14 people in the ALA PDT group, who received an average of 2.9 ALA PDT treatments, the study found. Improvement in acne lesions was visible within one to two weeks after the first treatment. No one in the control group achieved complete acne clearance.

The findings were to be presented March 5 in San Francisco at the annual meeting of the American Academy of Dermatology.

"The first-of-a-kind study found this particular form of photodynamic therapy used in conjunction with topical therapy to be the first such treatment to achieve complete clearance of acne up to 13 months post-treatment and a 77 percent clearance rate per treatment," the study's author, Dr. Macrene Alexiades-Armenakas, an assistant clinical professor of dermatology at Yale University School of Medicine, said in an academy news release.

"Patients also experienced an added benefit of significant improvement in their acne scars, as the pulsed dye laser offers superior penetration to the deeper layers of the skin where scars form," she added.

Mild redness that lasted for 48 hours was the only side effect, according to the study.

SOURCE: American Academy of Dermatology, news release, March 5, 2009