J.T.
Sounds like heat rash to me. My son has it too, as he sweats quite a bit while sleeping, even though I dress him lightly and keep the bedroom as cool as possible. His pediatrician saw it before and said it is nothing to worry about, just try to keep him cool. It does not itch, unless it is severe heat rash. I used Aloe Vera gel on him last summer when we were on vacation and he had severe heat rash that bothered him.
Answers to a similar question
http://www.mamapedia.com/questions/9089634658265726977
and a link from one of the answers to that question
http://www.babycenter.com/0_heat-rash_11436.bc