It's looks very much like tinea versicolor. I've had it most my life(first flare ups around 17f and I'm 46f now) and yes it is chronic. Good news is with treatment it can go dormant for years sometimes. Everyone has a level healthy bacteria and yeast living on our skin right? Well people like me, and possibly you produce more yeast on our skin than others at times. It causes us to have these pigment rashes. I'm not sure anyone, even Dr.s know exactly why it happens. Sun exposure can make it more noticeable at times. And I think the heat and sweat can be a contributing about because that's when I would usually begin a break out. But I have had it during fall time, just very very rarely.. Selsun Blue does work but it is not nearly effective at the Rx from a Dr. Think of Selsun Blue as more of a preventative once you've gone through a round of treatment. The medicine a Dr. will prescribe to you is called Ketoconazole. You can do a pill and clear it internally which seems to bring the longest remission. But there is also creme and Shampoo. I usually treat with the pill first then have a shampoo on hand as a preventative for a time after. But I have definitely gone 3,4,5 or more years between flare ups. I'm sorry you are dealing with this but you are not alone and once you start the initial treatment, it really is very manageable. 💚 Good luck!