Fractional CO2 Laser almost never leaves behind hypopigmentation
Traditional CO2 laser resurfacing works almost like blow torch where the entire epidermis and part of dermis (the level beneath top layers of the skin) get ablated and wound healing can last couple months; therefore the risk of hypopigmentation would be nontrivial.
On the other hand, Fractional CO2 Lasers such as Mixto, Active Fx, Fraxel Repair, work by creating microthermal zone (MTZ) so that adjacent skip sections of the skin that are not directly penetrated by Fractional CO2 laser will replenish one's natural pigmentation via intact melanocytes (pigment producing cells) so that hypopigmentation is almost unheard of and the wound healing process for the face is typically no more than 6-7 days for the face.
Microfractional Laser cannot cause hypopigmentation
Mixto Microfractional laser resurfacing burns extremely small holes in 20% of the treatment area. These holes instantly close.Therefore the top layer on the skin (epidermis) remains intact with a full complement of pigment producing cells ( Melanocytes). Thus, when it is used correctly , it cannot cause Hypo (decreased) pigmentation. The reason for confusion about Hypopigmentation is that the original CO2 lasers burned off the The entire epidermis destroying all of the pigment producing cells. If an unqulified physician went too deep while using traditional CO2 laser, hypopigmentation did occur. The Miracle of blending the CO2 laser with a scanner that produces Micro (extremely small) holes in only 20% (Fractional) of the treatment area Dramatically improved The world of Tightening, Smoothing, Lifting and removing Dark spots on the skin. Now, Patients can get up to 60% tightening, which can last as long as 15 years with only 7 days of painless recovery.
One of the major benefits of the Mixto laser, and others like it, is that the laser energy is "micro-fractionated", meaning that rather than treat every skin cell on the surface, it is mor like punching tiny little holes in the skin, so that some skin cells are not affected by the energy. This micro-fractionation also means that more of the color producing cells in the skin are left un-treated, so that changes in skin color with these lasers is very rare and not often an issue for most patients.
This is also the reason these lasers are safe to use off of the face, for treatment of the neck, chest, hands, or other areas of sun damage.