Does MiXto Laser Cause 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.

Hi there-
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.

Yes, the MiXto can cause small spots of lighter colored skin.  I have seen it when I use heavy setting and suspect it to be related to high treatment densities, possibly a heat injury to the melanocytes around the very small laser columns.  Most the time this has resolved, but I have a few patients that is a longstanding issue.  I have improved with IPL treatments to even the skin color and with a microlaser peel to even the texture.

In my experience, ANY laser can cause hypo or hyperpigmentation. It is true that the MIXTO has been designed to minimize this and other side effects that were more common with older CO2 lasers. A lot depends on the patient's skin type and tendencies and the depth and intensity of the laser. Patients at risk for pigmentation problems often benefit from pre and post procedure pigmentation stabilization programs. Thinner skin like necks seem to also be more sensitive than facial skin to pigmentation issues. 

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.