My child clenches his teeth and holds his breath when he gets angry. is this normal?

Tantrum varient: You are describing a tantrum varient of childhood loosly called "breathholding spells".Rare but occasional in infants it peaks around 2 & fades by school age in most.Often triggered by a scolding or your refusal to comply with their requests, they can turn blue, pass out & twitch.It is not a seizure & they self recover.Avoid locking eyes but monitor them.Don't reinforce the behavior by cuddeling.

The point of anger..: ...Is to get you to change what you are about to do. Children will often repeat behaviors that have successfully got your attention in the past - which, i would guess, included a fairly significant reaction to clenching teeth. Breath-holding may actually be natural, as a consequence of hyperventilation while screaming.

Ignore It: The purpose of a tantrum, even involuntary, is to obtain a goal. Ignoring it teaches the child that this action gains no reward. Even if they turn blue!! The brain will naturally protect the child from damage. When done, give them a hug, reinforcing the "good " behavior. Over a period of 2-3 weeks, if consistent, the tantrums will lessen in frequency and severity.