PPx is a ligt based therapy similar to IPL--Intense Pulsed Light.
Any light therapy can cause side effects if not used properly.
Results are usually seen after 5-6 weeks and ususlaly multiple treatments are needed.
When you are exposed to the sun, freckles will come back.
If your freckles are true freckles and not sun damage--the pigment goes deep and is unlikely to be completely removed by any light therapy.
If PPx treatments are done at too high a power setting or too agresively, the skin can be burned which can lead to scarring--this is true with any light or laser or IPL therapy.
Complications are caused by the user-not the machine.