Why does screaming make me lightheaded?

Dizzy /screaming: Related to breathing mechanics. You are either hyperventilating at the time or not breathing properly You are also increasing neck/laryngeal/diaphragmatic muscle strain and using a lot of oxygen. And I wonder if there may be an increase in intracranial pressure

Depends: People scream for different reasons, eg, fear, excitement, frustration, rage. That said, adrenaline surges may be causing physical symptoms including feeling lightheaded. Try to tone down the screaming if possible. Take a time out, walk away or avoid high stress situations. Your body may benefit.