OK, so the title is a little melodramatic.... But I thought this post may help some people.
I was using an Ego and 510 with various e-liquid from various vendors. I started getting sores in my mouth. I thought my problem might be that I had some atty's that were going out/clogged and I was sucking on the e-cig too hard. I replaced the atty's and got bigger vapor but was still getting sores in my mouth like crazy. Once or twice I really burnt my tongue bad somehow (Heat? Chemical?) I suspect the whole "I can't taste anything anymore" is related. Seriously, it didn't matter what juice I used. It wasn't like that when I started vaping.
For the life of me, I couldn't figure out what I was doing different. And it wasn't like an infection at all. It was like being burnt with heat or chemicals, slowly..... over days.
Then my mod showed up. I got a black/black Reo Grand. It makes mountains of vapor with no effort. For some reason all the sores in my mouth went away. And what is crazy is that the mod puts out way more vapor/chemicals. So, I don't think it is the e-juice makeup that caused the sores.
Heated Micro Spheres of Death:
The only thing I can think of as a cause is this: I would start vaping with an Ego or 510. In a attempt to get more more vapor I would unconsciously suck harder on the e-cig. This would cause heated vapor to enter my mouth and burn me. Perhaps it was just little micro spheres of heated vapor. I never felt that I was being burnt when it was happening. It would take a day or so for sores to show up.
But with the mod I have all the vapor I want and thus don't hardly drawl on the mod at all.
I think if you hit an e-cig hard and try to drawl vapor from it that small heated vapor droplets burn your mouth and tongue. I think in the short run you can loose your taste and over a couple of days it can cause sores in your mouth or on your tongue.
The fix for me was to get a better e-cig that i didn't have to drawl on. Your mileage may vary...
All of this is pure speculation. But I think that heated micro spheres of liquid/vapor is a good candidate for what I have experienced and what I hear from others. I think a 2 or 3 inch extension would not be out of the question. Perhaps even a mesh screen to help cool the vapor. I may try this with my Ego and 510's. It probably wouldn't hurt to use it on my mod as well.