Melasma causes brown to grey-brown patches on the face, it affects mostly women and is caused by genetics or hormone imbalance.
In the comments section of the article you can find non-chemical solutions that have worked for other women.
Melasma has been linked to thyroid, estrogen/progesterone and adrenal imbalances.
Along with topical solutions consider looking into the imbalances mentioned above as part of your treatment plan.