What Causes Bumps On Frenulum Of Penis?

well its this guy that has bumps on the frendlum of his penis. They dont irritate him, because he didnt know they were there until i pointed them out. So now he is all worried and stressed out. They didnt look like anything out of the ordinary. They didnt look like anything to stress over, but you never know. There want like ALOT of them, it was like a few may be like 3 or something. Can i have an idea on what this is??