FWIW my $0.02 (worth BOTH pennies)
I have ridden with a guy who always has 100% of his skin covered all year (central alley CA summers, so >110F) I asked and he has a skin issue, cancer survivor, or some sensitivity. I looked into it at the time, and you can buy ($$) purpose made coverings from a medical supply store. if you have a Rx, insurance might even help out.