Acne scars are the result of damage to the protein collagen of the skin.  Ablative laser therapy has led to the best results by heating and removing the outer layer of skin.  Unfortunately, there is usually a 7 to 10 day recovery period after treatment with a prolonged redness in the skin and a risk of pigmentary changes.

Nonablative laser therapy works beneath the surface skin layer to stimulate collagen growth, which helps improve scarring as well as minimize fine lines. Each nonablative laser treatment costs $400-$600 per session and usually five are required.

Nonablative Therapy Good Results: 11 people with mild-to-moderate acne scars had a 10% skin improvement after three treatments.  However, one month after the fifth treatment, improvement rates rose to 23%. And at six months, there was a 40% decrease in skin roughness due to continuing skin collagen remodeling. Some nonablative laser treatments also appear to work by shrinking oil-producing glands in the skin. Paul M. Friedman, Houston, Archives of Dermatology, November 2004.

Cold-Air Cooling Reduces Pain and Recovery in Ablative Laser Acne Scar Resurfacing: Ablative skin resurfacing with carbon dioxide (CO(2)) and erbium:YAG lasers is the gold standard for treating rhytides, photodamage, and acne scars. However,  downtime and pain are significant drawbacks. In a 6-month study of 8 patients treated with single-pass CO(2) laser skin resurfacing of wrinkles around the mouth and eyes, during laser treatment, only the right half of each face was cooled using a cold-air system. A mild improvement of the wrinkles was observed in all cases. The use of cold-air cooling did not have any impact on the long-term results, although in a direct comparison between sides, it was observed that cooling reduced the recovery period from 3.9 days to 3.5 days (P = .09) and helped postoperative redness fade more quickly, from an average of 21 days to 11 days (P = .17). The reduction of pain was significant, which led to a much higher level of patient acceptance: on a numerical analog scale of 1 to 10, the rate decreased from an average of 6.8 to 3.6 (P = .006). Single-Pass Carbon Dioxide Laser Skin Resurfacing Combined With Cold-Air Cooling: Efficacy and Patient Satisfaction of a Prospective Side-by-Side Study. Raulin C, Grema H., Karlsruhe, Germany. Arch Dermatol. 2004 Nov;140(11):1333-6.