I'm using a lotion CLAIRMEN which contains hydroquinone,is there any one can explain how does the chemical affect?

Hydroquinone is a mild oxidizing agent. It reduces the formation of melanin in the skin. For that reason, it's used for reducing the effect of freckles and things like that.

Hyrdroquinone reduces menlin like perito said. It can be very harmful for some skin types. It is in a lot of skin lightening products. You can read a little more about it here:http://http://en.wikipedia.org/wiki/Skin_lightening