I've been shopping for hair dryers and in all malls I've been to the salespeople explained how the "ionizing" hair dryers are better than the ones without that function, because it makes your hair less frizzy. I have been able to talk four of about twelve of them to come clean with me and tell me if they actually knew the science behind that, and they said they didn't really know how that works, but they were instructed to tell that to customers to sell more of these new, more expensive dryers.
Reading up a bit on how the fans and dryers work, turns out they tend to make the air passing through them leave electrons on the encasing, and the air coming out of them is slightly positively charged. So to negate that, hair dryers have negative ion generators like YFA-114 variants from Youji.
I have been drying my hair with the old non-ionizing and the new ionizing dryers and I haven't noticed any difference with my hair length (~15cm). Maybe it matters more with longer hair, but I asked girls with longer hair to try these out and they said they didn't notice any difference between them either. Maybe my hair dryer doesn't have a working ionizing element, maybe we're just not seeing the difference, or maybe it's just a marketing trick.
There's also an awkward situation when sometimes you want to get more volume in your hair, so you'd want to turn off the negative ionizer. I've seen some hair dryers on the internet stores have a switch for it, but most don't, leaving you less options. If so many people would have bought those dryers and had problems with achieving volume, you'd think it would be something people talked about, but that's not the case. Perhaps because there's no actual difference at all.
Do these fans actually ionize anything? Is it really helping reduce hair frizziness? If it doesn't work, why not, and how would it work in theory?