I developed those too with the change in diet-but not on my arms.. I had them right above my cleavage. I thought I had them because of gym--i sweated alot one day & nxt day these rashes & they kept increasing
So i was scared to step on the elliptical after that lol.
But I did make a docs appointment, and he said they are also called diaper rash & gave me some nightsatin anti fungal cream--and the rashes/spots r finally going away! still can't fig out how they happened though, because I have been going to gym for 1 month.
Jus get the anti-fungal cream from ur doc & they'll go away--if they are the same thing as mine