Solution for Dark Mosquito Bite Scars on Legs?

I frequently see patients with dark spots on their legs as a result of mosquito bites, scratches, or generalized eczema. These hyperpigmented scars can be improved by a regimen of prescription topical hydroquinone and retinoids. I also recommend a chemical peel to expedite the process of color equilibration.
At this time, I would recommend  Melarase , including Melarase AM and Melarase PM. This should help lighten and even out the dark spots on the legs.

It is difficult to know what is the exact cause. Generally prolonged inflammation may produce hyperpigmentation that typically resolves with time. This is not necessarily the same as hormone induced hyperpigmentation. It may benefit from bleaching agents. However it may require more agressive treatments.
I would recommend seeking the services of a dermatologist to discuss your options.