Why does my nose itch when i brush my teeth with powder?

Irritation: You may be breathing in some of the powder and it is irritating your nose. Maybe there is an allergy to the powder.

Don't inhale: You don't say what powder you use. But it really doesn't matter. You might be inhaling as you get your powder filled toothbrush near your mouth. So...Hold your breath a few moments. Or..There is a connection between your moth and nasal cavity...You know..Milk out your nose at the wrong time. It might just be easier to switch to a paste or just use plain water or mouthwash to brush your teeth.