How long after a CO2 laser treatment should I wait before starting a series of non-ablative fractional laser treatments?

Thank you for your question. You state  for your acne scars, after you underwent CO2 laser treatment you became aware the treatment was about 50% effective in improving acne scars, so you want to know when to follow-up the treatment with a 1540nm laser, and how long after initial treatment can you do that.
I can share with you the principles that are relevant with this type of question. A little background: I’m a Board-certified cosmetic surgeon and Fellowship-trained oculofacial plastic and reconstructive surgeon. I have been in practice in Manhattan and Long Island for over 20 years. I have been using lasers since the early to mid 90s including the original CO2 ablative lasers, and it’s a time in laser treatment when we have so many options. When you have these many options, you also understand there’s clearly no single best approach to any particular problem.
Acne scars are one of the most challenging problems to treat. You have to think about someone who can manage you from all aspects, and not just treat you with the laser. The reason is most people who have acne scars have a combination of scars, from rolling scars, boxcar scars, ice pick scars, atrophic scars, to facial fat atrophy.
Before you start with any laser, what I do is look at the foundation of what gives a person smooth looking skin. People think it’s all about trying to smooth out the top layer, but when you think about skin, you get a structure that’s about 2 millimeters in thickness in the face. You also have to think about volume below the skin.
When you ask a question like this, I hope you’ve also had a discussion with the physician about strategies. When I evaluate a patient with acne scars, I take photos with direct light, and I take photos with backlight. Backlighting shows me areas which cast a significant shadow. Often I find the most significant shadows are cast because of volume loss.  What I often do for a younger person is Structural Volumizing, which is placing a long lasting filler like Juvederm Ultra Plus and Juvederm Voluma at the cheek level, on the bone which results in a restoration of volume so acne scars look smoother. A lot of patients who come in who have experienced facial aging on top of acne scars really appreciate that significant change, probably more than anybody. The point is understanding you have to work from the inside, then outward.
We also combine other treatments to improve the skin’s ability to respond, so I sometimes combine this with platelet-rich plasma (PRP) injection, or microneedling with platelet-rich plasma. I try to minimize more aggressive ablative procedures, so before doing them we get the skin healthy and full, so you may end up needing more conservative treatment.
There’s a basic principle in wound healing where after you have an injury including the controlled injury of laser resurfacing, there is a proliferative phase of generating collagen that lasts about a month. Based on that concept, it might be safe for you to do a non-ablative procedure such as this particular laser to try to stimulate collagen. I would caution you that there’s also a wound remodeling phase. I would lean more on the conservative before trying to stimulate the skin to generate more collagen because you can only generate so much. Often, people are frustrated because they get a laser, and another laser, and another to the point where they have come to me, and their skin after so many different laser treatments looks really thin. We then do tissue rehab where we’re using platelet-rich plasma derived from your blood, sometimes combined with Acellular matrix to help stimulate the fat cells and give the skin some substance before treating it with another laser. Interestingly, the world is coming full circle with a lot of the luminaries who were the biggest proponents for laser are now advocating PRP as well as microneedling.
I think you have to think through this process and have a realistic understanding of outcome. People generally want to see significant improvement. Often, acne scar patients get very frustrated because they don’t necessarily see improvement, they only see where there’s still loss. It’s very important to have a good relationship with your doctor, and have clarity with what the outcomes will be, and the timing. We have a lot of tools, but you have to know when to use them, and when to hold back and wait. Ultimately, it’s my goal to do what is most effective, with the least amount of downtime, and have a sense of what makes the most impact. Unfortunately, you have to accept there’s no perfect solution for acne scars. There are ways to treat and improve appearance, but some things cannot be completely reversed. I hope that was helpful, I wish you the best of luck and thank you for your question.

In general, its 4-6 weeks but you really should check with your treating provider as there are certain issues like delayed healing that may be a factor in delaying further treatments. 

I recommend following up with your Doctor about the recommended timeline for fractional laser treatments after Co2. Keep in mind, it will take several weeks for the Co2 laser results to settle. Acne scars need a combination approach with lasers, microneedling/prp, Cosmelan subcision and fillers. I recommend getting a formal evaluation with a cosmetic dermatologist. Best, Dr. Emer