Are skin lightening creams harmful to our health?

I am not going to run down any product - but if I were you, I would like very definitely to check the constituents of the medication I am applying to my face. All the feel good messages like making your skin fair without any side effects do not cut ice with the medical community and these companies should be encouraged to divulge the formulations to the public and answer queries as to how each constituent works and whether any one of the constituents could have a side effect.