For what it's worth, almost 20 years ago I started getting this itch on the bottom on my foot. It was only at the end of the day after I'd taken my socks off and was in bed. And it was only in the summer. Usually would itch like hell for 10 to 30 minutes and then go away. I noticed it very very slowly got worse. And eventually went up to my groin area over the course of many years. And again, only in the summer, and only at the end of the day after I was in bed. I tried tea tree, etc and it made no difference.
Shortly after going vegan 8 years ago, I started eating a lot of blueberries at times. And over the last 8 years I've noticed when I'm eating blueberries I don't have this issue. If I get away from eating them, it comes back. Although, again, only in the summer and only at the end of the day after I've disrobed and gotten in bed.
I do have a bit of a toenail issue which is probably related. God I'm disgusting. I notice that clears to an extent with high blueberry consumption. Although, never has completely gone away.
Probably from showering in gyms.