What Causes A Brown Colored Skin Rash On The Hips And Underarms?

Hello there,Good afternoon,My question is about my skin rash.At first it look round and reddish and it only appears in my neck, but after a few weeks it became bigger, the color changed into brown and I noticed that my underarms and hip were infected too although it s not itchy. I got this a few months ago, and then after a month it disappeared. And last week I notice that It went back and this time it s even worse. Is this a ringworm? Are there any foods that I m not allowed to eat?Any advice?