Me and Modern Toothpaste: Human Research Participant

A couple of years ago, during a cold snap in winter, I noticed my hands were getting acutely chapped, with cracking of the skin and bleeding.
I come from a cold climate, I had never had problems with cold weather before.

Ah well, thought I, getting old; too much time in California made me soft.

So, I made a point of wearing gloves or mittens, even when the temperature was barely below freezing. Hands still hurt when it got cold, but it helped.

However, later that winter, I was traveling to an even colder, windier, clime, and I noticed my hands were fine. It was as if I had discovered some fountain of youth...
Well, no. But, I did wonder.

Two things struck me, I tended to preferentially have cracking and bleeding on the thumb and first two fingers of my right hand, and preferentially on the middle knuckle.
Then, one morning, I noticed that the froth from my toothpaste lay right across where the skin was worst - what can I say, I like to use lots of toothpaste and I wet it before brushing.

Secondly, my traveling toothpaste was different from my home toothpaste. The traveling toothpaste was one of the microsized old style toothpastes; at home we had switched to a new "whitener" toothpaste.
I'd blame the switch on too much coffee, but honestly I think it was primarily because it was nigh impossible to find any toothpaste that didn't have whitener in it. And it was new! Different! Better! More Heavily Advertised!

Hah! Thought I.
Eureka!
I have a theory. Or at least a weak conjecture based on anecdotal data with a sample of one.
That is enough for a theory.

So, as an experiment, I started using regular toothpaste again at home, and, voila, my hands were fine. (Except for the cramps from having to fill out all the associated paperwork).
Of course the next winter wasn't that cold... and I had got in the habit of wearing gloves... but, dammitt, my theory worked!

Time passed.
I went to see the dentist.

As I was leaving, I asked: ...blah, blah, hands chapped in winter... blah blah, switched toothpaste... blah, blah. Heh, it couldn't have been the whitener toothpaste, eh?

"Sure it was", says he.
Damn thing has peroxide, it strips the oils off your skin where it lays on it, leaves the skin dry and it cracks like a rotten twig, come the first frost... (I paraphrase here).

Wot? Thought I? So, I'm not, like, crazy...?

Well, apparently I am not crazy, and whitener toothpaste, if you let it bubble over your skin, will dry the skin out severely and leave your skin dried, cracked and possibly bleeding as you head out into the bitter cold Pennsylvania Winter Morning.

Or so say I, and my anonymous dentist.

I did of course google this:

the styleist blog blames whitener toothpaste on bad skin...

tipking recommends daubing it on zits - burns them off, apparently, if you can stand the pain

ok, not exactly what I was after, but suggestive of some effect of toothpaste on skin.