Greetings. If I have under stood right, you might be talking of skin darkening in an area after fungal infection. This is called post inflammatory hyper pigmentation. It's important to get the infection cleared completely before the pigmentation can be treated. Onabet doesn't work specifically for pigmentation but rather on the fungal infection. Pigmentation will reduce slowly. See a qualified dermatologist near you. Further queries may be sent on follow up messaging.