Are "ionizing" hair dryers any different from the regular ones?
All you need is alternating HV switch between pins to create a flood of +/- ions to neutralize static in dry hair. In wet hair, it makes little difference. 1Hz or faster is adequate at 1pps to allow charger to build up hiV at 1kV/mm min from sharp tungsten pins or SS needles.

Dry air from p-p or point to point BDV or breakdown voltage at sealevel is ~1kV/mm then rises to 3kV/mm for plane-plane. It reduces &lt; 1kV/mm with dust and humidity.

We used these in clean rooms to make dust fall to floor but they arc at broad spectrum with recursive notches in spectrum matching wavelength in the gap and screwed up EMI in our magnetic disk servo writers so they got tossed in the garbage.

The so-called negative ion ionzers may not work if the tribo-electric voltage or static voltage is not positive static from the compatible materials of plastic brushes and hair.  I would suggest they cannot balance the charge and only alternating voltage ionizers can work effectively. 

Normally electrons escape from the better "conductor" of the two "insulators". to create a positive static voltage when energized by friction.  this is ion flow analysis 101... ;)