Hi there,
Scarring after appropriately administered fractional laser skin resurfacing is uncommon due to the high safety profile of this modality of treatment. Nevertheless, scarring may occurs due to several more common factors. These include:
1) Aggressive treatment parameters (use of high energy and/or high density settings) especially when treating non-facial sites such as the neck, causing excessively deep skin injury.
2) Secondary bacterial infection due to suboptimal post-laser skin care or from repeated picking on the healing skin scabs.
3) Herpes simplex virus (cold sore virus) reactivation following skin injury from the laser treatment.
This complication is preventable by the use of oral antivirals such as Valtrex given 1 day before followed by several days after treatment. The risk of scarring post-laser resurfacing may be minimized by choosing an experienced laser doctor, informing him or her if you have a past history of cold sores, and taking care of the skin well after the procedure.
Hope this helps!