Microwave hair removal
Extremely limited data on safety and effectiveness (especially for use on the face) make this a device to avoid until there’s more data.
Microwave radiation is sent through a handpiece into the skin, where the energy causes thermal damage.
Targets all colors of hair.
Targets everything else in the skin, too.
Not cleared for use on the face.
Not enough data on safety or effectiveness.
“Delivers precise, controlled pulses to the hair follicle.” (Pulses are delivered all tissue nonselectively.)
“Causes destruction of the follicle without damage to the surrounding skin.” (There is no published data showing this device causes destruction of the follicle, let alone selective destruction. They offer no explanation why the device will spare other moisture-containing structures and substances in the skin.)
This device uses microwaves like the kind used in a microwave oven. Microwaves are just radio waves (within a certain frequency range) that have an interesting property– they are absorbed by water, fats and sugars. When they are absorbed, they cause molecules to vibrate, which results in heat.
Here’s the problem and potential danger with microwaves: microwaves can heat ALL the water and fat in your skin, not just the parts near the hairs.
The primary difficulty in hair removal is delivering enough energy to the hair structures to cause permanent damage without damaging the surrounding tissue. Frequencies in the microwave range have been shown to be effective when conducted down a metal probe. This is how the type of needle epilation called thermolysis works. The damage occurs only to the areas of the hair follicle right around the metal probe.
Unlike lasers, a microwave does not rely on selective photothermolysis. Microwaves don’t heat up a target (like laser do to melanin) while sparing other structures. This indiscriminate heating of all water and fat in the skin is potentially problematic. To generate enough heat to damage a hair follicle, a microwave might also generate enough heat to destroy other things like blood and sweat or oil glands needed to keep skin healthy. In addition, there is a very real possibility of causing eye damage from microwaves directed at the face. 
Until there is published data on these devices, the danger of collateral skin damage represents an unknown risk. I urge all consumers and practitioners to avoid using this device until there is more information.
In 1999, FDA cleared these devices, but they specifically stated they are not to be used on the face.  One company in the US has been cleared to sell these devices, but they have sold very few of them. 
There is no published clinical data on safety or effectiveness of microwaves delivered in this manner for hair removal.
Again, I strongly recommend that consumers avoid microwave hair removal until there is some published clinical data demonstrating the devices are safe and effective for hair removal.