These sit at opposite ends of the same category. Moxi is about as gentle as resurfacing gets. A fractional CO2 laser is about as aggressive as it gets.
The difference is whether the surface is removed. Moxi is non-ablative — it heats columns of tissue under the skin and leaves the surface intact. CO2 is ablative — it vaporises microscopic columns of skin, surface included.
That decides the downtime and the result. Moxi costs you a few days looking sunburnt and sandpapery. CO2 costs you a week or two of real recovery, and does considerably more for deep lines and scarring.
A thulium laser at 1927 nm, absorbed by water very near the surface.
Vaporises microscopic columns of tissue.
Lentigines, solar lentigines and freckles are named in the clearance.
It works in and just under the epidermis.
Which is why it can remodel scars and deep lines.
Most people are presentable within a few days.
In a retrospective study of 856 non-ablative fractional treatments — mostly at 1550 nm, in Fitzpatrick III–IV skin — about 5% had a side effect and darkening afterwards occurred in about 1%.
Longer healing means more opportunity for infection and scarring. The complication that defines this treatment is delayed hypopigmentation — patches that are permanently lighter, appearing months afterwards. Prolonged redness lasting weeks to months is also common.
Look at what actually bothers you in the mirror.
Colour — brown spots, freckling, a dull uneven surface. Moxi is built for this, and it is what its clearance names.
Structure — deep lines, indented acne scars, crepey texture. Moxi will soften these a little at best. CO2 is the tool that changes them.
If you are not sure which category your complaint falls into, that is a good question for a consultation rather than a booking.
Ablative resurfacing is an effective treatment with real complications, and they deserve naming rather than a phrase like "pigment change."
None of this is a reason to avoid CO2 where it is the right tool. It is a reason to have the conversation properly.
Any laser that heats pigment can also provoke pigment. In deeper skin tones, the risk of darkening after treatment is higher, and it rises with how aggressive the treatment is.
That is not a reason to rule either out. It is a reason to see someone who treats your skin tone often, and to ask directly what settings and what pre-treatment they use.
If you get cold sores, tell your provider. Both treatments can reactivate the virus, and before ablative resurfacing in particular, antiviral medication started in advance is standard.