Hi Zöe,
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I wouldn't pay their advice on which method is better too seriously, unless they're adept at
using both methods themselves. It's a sales pitch, nothing more...and they want your business.
My electrologist did the same thing. I don't know anyone who has gone straight galvanic, but between blend and thermolysis, either method works fine...as long as you have an experienced technician.
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As for your previous treatments with galvanic, I'd be concerned that you were wasting your money
with someone that wasn't putting the machine high enough to kill your hairs. While it doesn't need
to be excruciating, you should feel some pain/discomfort during treatment...especially around the lips and other sensitive spots.
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As for my own experience, I've had about 350 hours of flash thermolysis in the past 3 years.
(almost done, thankfully

) No scarring to speak of. She's a little slower than I'd like, but my electrologist has done a good job. Like you, I was very concerned about any scarring or pitting on my face, so I went with cautious experience over speed...and I'm happy with the results.

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The redness is normal. I often have little red dots like those seen on your chin, along with the accompaning blushed area around it. That stuff heals up just fine. I usually get 2 hours of treatment every Friday night, and during the worst weeks it'll still look a little red and irritated by work on Monday, but not enough for people to think that it's anything other than a bad case of razor burn.
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The swelling after 2 days is a bit concerning. The white blisters I would be even more concerned about. We are talking about heat blisters, and not little whiteheads from infection, yes? If these are little white pimples that you can just pop with a pin and squeeze out, then I'd suggest being more carful with your aftercare regimen. (I would regulary wipe my face with an astringent like witch hazel 2-3 times/day to keep the pimples from coming)
If they're heat blisters though, find a different technician.
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A couple of questions to help clarify things:
How many hours did you have done in that session?
Was it all in the same area (the chin)?
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I know some people that have gone to E3000 (blend method) and gotten a lot done at one time. They do look rather red and swollen for quite some time afterward...even after a week's time. So how much treatment you had done is a consideration in gauging the reaction of your skin. If you had a large amount of time done in a small area of skin, the swelling you've seen may be normal. Heat blisters, however, are not normal. But to put your mind at ease, looking at your pic, you should heal up just fine. I don't think you've done any permanent damage.
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Regarding blistering though, there's more to it than just monitoring the level of the machine.
A technician also has to consider how close together their zaps are. My beard was very thick, coarse, and dense when I started...the triple whammy. Often I had 4 hairs growing out of the same place in all sorts of directions. To make sure she didn't damage my skin, my electrologist had to thin the area out first, else risk damaging the skin by treating the same small area with too many zaps in too short a timeframe. Just another thing to consider depending on your skin type and hair distribution. If your hair is similar to mine, a more conservative approach might be warranted (even if it might cost a little more, or take a little more time. You only have one face, so you need to take care of it.

at least...that's how I look at it.).
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Hope this helps,
Best of luck,
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Kaitlyn (Kay)