another thought is that synthetic sweeteners increase the sensitivity of the skin to sun. This may not be a cure but you could do worse than cut out all of the synthetic sweeteners. It will take a long time before you see any difference, but for me, at least, the change is noticable on my arms and on my face. I will add that I was not suffering from hyperpicmentation but definitely showing larger and larger " age spots." which have since declined and ceased as long as I am systematic with sun screen before, during and after the ride.
marni
marni
Katy, Texas
Trek Madone 6.5- "Red"
Trek Pilot 5.2- " Bebe"
"easily outrun by a chihuahua."