Using a hair dryer is good for your hair as long as you use the hair dryer properly and not hold the hair dryer too close to your hair when drying it.
When holding a hair dryer to close to your hair it can dry the hair too fast and cause damage to your hair but holding the hair dryer out far enough will prevent damage from your hair dryer to your hair.
I use a hair dryer every time I wash my hair and hold the hair drier away from my hair at arms length and my hair dries just fine without damage.
Hair dryers that professional hair stylists use are Dyson Supersonic Hair Dryer, GHD Air Hair Dryer, GHD Helios Hair dryers.
Some professional hair stylists use more expensive hair dryers and those hair dryers listed above range in cost from $400.00 to as low as $180.00
The Dyson Supersonic Hair Dryer is a good hair dryer that my hair stylist used on me.
But for me that hair dryer is too expensive for personal use.
I would not want to pay $400.00 for a hair dryer.
The cheap Walmart brand of Hair dryers work just as well as the more expensive ones do.
But if you're a professional hair stylists or barber that cuts hair then using a high quality more expensive hair dryer could be worth it.