What Causes Tiny Red Bumps On Left Side?

my wife is 22 120 pounds 5ft an has tiny red bumps under left arm an on her side, she went to doctors office about a month ago an he gave her a creme an it went away now its back butt only on her left side this time, some have tiny white pimple like heads, she has had staph befor from a spider bite if thats any consulation to the problem