K.G.
My son is 3.5 and I still don't let him chew gum.. He has some friends his age that do and has asked a few times but I always tell him "when he gets to be a bigger boy he can" and he's totally fine with that.. If I can help it, I prefer for him not to chew gum...
I think I'm more nervous because when I was young I used to chew a ton of it and ALWAYS swallow it... One night I swallowed so much gum (gumball machine at my friends house) that I was sick puking for a whole entire night..
There's not a lot of benefits from gum, so if I can keep him away from it, I will. He's not "super interested" in it though so its easier for me..