What can help fade away my mom's skin problem?

My mom used to have acne and have face creams that helped with it. About a year ago, the usual face cream she bought had a new formula and without the skin care place informing my mom, she have light brown patches on her face. It's not like there's a lot of spots on her face. It's more like a very light brown patch about the size of a quarter on each of her cheeks. It's pretty noticeable in the sun and she's embarrassed by it. Does anybody know how to fade away the patches or what skin problem she is having? Thanks.