how did i give myself this freckle?

April 8, 2007 4:57 PM

is there a chemical that can permanently stain skin brown, or induce a freckle?

about fifteen years ago, in my high school chemistry class, we were doing an experiment with a chemical that our teacher warned us would stain our skin. i got a drop of it on my palm and have had a freckle in that spot ever since. (i wish i could upload a picture but my camera doesn't have good enough resolution to show the detail.) it's the same color as my other freckles, but it's not natural--you can see where the liquid ran and settled into the tiny lines on my palm, leaving the ridges unstained. it's about 1/8" in diameter.

my question is: what could this chemical have been? obviously it's more than a surface stain, since it's been there for fifteen years. my guess is that it had to be something that would stimulate melanin production on contact. any ideas?

posted by thinkingwoman to Science & Nature (16 answers total)

Phenol can cause chemical burns that discolour (gets darker, like a light mole or a freckle) but my phenol burn discolouration from undergrad went away within weeks.

Oddly, my phenol burn when I was a research associate didn't discolour and wasn't nearly as severe (maybe the difference between being buffered or not?).

Silver nitrate will also cause discolouration but it tends to be darker and unless there is damage to the skin (like in tatooing) the discolouration goes away within a week or so.
posted by porpoise at 5:07 PM on April 8, 2007

Don't know the chemical, but it doesn't have to be a melanin stimulating factor. It was probably some dye, dissolved in an organic solvent, most likely DMSO.
posted by kisch mokusch at 5:15 PM on April 8, 2007

We always got that warning with silver nitrate in AP Chem. There's a picture here.
posted by Mach5 at 6:49 PM on April 8, 2007

It was probably silver nitrate. I got the stuff all over my hands in a chemistry course and didn't know about it until the next day, when some odd blob shaped brown discolorations appeared on my hands. The stains disappeared in about a week.

It may be that you had a cut on your hand and the AgNO3 was able to get down beneath the layers of the skin that slough off.

However, it seems more likely to me that the freckle was always there and its odd shape has to do with the fact that the ridges of you hand are subject to more abrasion than the furrows. You never would have taken any notice of the freckle if it were not for the fact that you accidentally satined the same spot on your hand with a chemical.
posted by 517 at 7:07 PM on April 8, 2007

Speaking as someone who is naturally freckled, you do not get freckles on the palms of your hands. I've got them nearly everywhere, but not there.

A silver nitrate stain is black, not brown, and it eventually wears off. (Based on my personal experience.)
posted by Steven C. Den Beste at 7:26 PM on April 8, 2007

Response by poster: no, the freckle wasn't always there. it is dark brown, almost round (it's got a little comma tail where it dripped) and there's no perceptible texture.
posted by thinkingwoman at 7:40 PM on April 8, 2007

You would've had to have had a cut there, or the chemical had to burn thru your upper layer of skin. Any stain on the top layers of skin would just disappear as those skins cells got replaced. I had a cut on my finger once that cause a mole like spot (blood trapped below) for about 5 years or so.
posted by muddylemon at 7:44 PM on April 8, 2007

I don't agree about the "no freckles on palms". I've got a natural one on the bottom of my foot.

Out of curiosity, was it painful or did it just leave a stain?
posted by nat at 11:42 PM on April 8, 2007

I don't know if this helps, but I 'grew' a freckle on the palms of each of my hands after accidentally stabbing myself with a pencil (two separate occasions, years apart- I'm clumsy). I doubt that the pencil lead had anything to do with it, but something to do with the event led to me growing those freckles on my palms.
posted by tumbleweedjack at 11:44 PM on April 8, 2007

I am naturally freckled and have one freckle on the palm of my hand.
posted by DOUBLE A SIDE at 1:14 AM on April 9, 2007

I got a silver nitrate stain in high school chem. Black initially, eventually dark brown. But 517 and muddylemon are right about it wearing off.
posted by eritain at 5:46 AM on April 9, 2007

Definitely NOT silver nitrate. My 8th grade chemistry teacher was throwing out outdated chemicals including a full bottle of AgNO3. I wrote up a lab proposal to deposit all the silver using electrolysis and collected it in through filter paper. I squeezed out all the excess liquid and washed my hands thoroughly. Later in the day they turned black with a slight purple tinge. Went away as my skin shed - in about two weeks.

As a side note, I freaked when I saw it - went to the nurse who had served as a nurse in Great Britain in WWII and when we went over my day, she said "Of course! I've seen this from soldiers in the war doing photography."

I can't say what it was - anything brownish I've used hasn't stained me for life (ie, iodine, FeII and FeIII chlorides, etc), but I'd vote for an Fe compound that went subdermal on you.
posted by plinth at 6:32 AM on April 9, 2007

Nitric acid burns will give a brown (and itchy) stain, but again, it should go away in a couple of weeks. Silver nitrate is the most likely culprit for the inital stain. The stain, as has been noted above, is originally more black/purple, but it does look browner as the top layers start to slough off.
posted by janell at 8:13 AM on April 9, 2007

i have a natural freckle on the palm of my hand, in the meaty part right below my thumb. It also has the lines in it that follow the creases in my skin too, as though stain had soaked in.

i vote it was an undiscovered natural freckle since i know nothing about the science of unnatural freckle making but it sounds like an abomination.
posted by ZackTM at 11:12 AM on April 9, 2007

Potassium Permanganate? Wikipedia states that skin stains disappear within 48h, but I'm sure that I recall being told that it was permanent...

Don't suppose that after all this time you can remember anything about the experiment?
posted by Chunder at 4:26 AM on April 10, 2007

picric acid?
posted by porpoise at 7:56 AM on April 17, 2007