. I Have A German Exchabge Student, Teen Boy Here

. i have a german exchabge student, teen boy here about 2 weeks now. the group has been outdoors a lot and been eaten by bugs, but tonight he has single spots all over his legs and arms about the size of a pencil eraser. they do not itch, he does not have a fever. he was at a lake today and used someone elses sunscreen. they are only where his skin was exposed. should I be nervous? Whay signs do I look for to show more concern?