Another possibility is heat rash. They dress the babies very warmly in Guatemala (probably an understatement) and it is not uncommon for them get heat rash. I bet it was 80 degrees when my son's FM picked him up from our hotel and she added a hooded sweat suit over his long sleeved shirt and pants and then she wrapped him in a thick fleece blanket! He was sweating bullets before she ever walked out the door!
Two sets of clothes, one being a sweat suit, a hat, hood and fleece blankie! Talk about snug as a bug in a rug! *hehe*
I gave her two huge tubes of rash cream in anticipation of the inevitable.
