R.D.
Why do they? To give us heart attacks and gray hairs ;)
My 5 year old was and my 15 month old is, a breath holder. It freaks my fiance out but I've seen it so many times that I think it's kind of funny. 'Aaaand, BREATHE!!' I know the exact shade of blue they turn before breathing. I also know that if they DON'T, they pass out and their little bodies simply reset themselves. My little brother used to hold his breath until he passed out! (Probably lost a lot of brain cells doing that, and it explains why he is the way he is now, LOL!!)
I think I also make light of it because I'm very confident in my CPR and the call response time for the paramedics in my area ;)