Several weeks ago my wife dragged a 14K gold ring across her check, leaving a bluish-gray trail. She told me this was a sign of anemia. After several weeks of taking an iron supplement, she can no longer make the trail. And she claims the test only works with 14K gold.

Any truth to this? If so, why does it work?

I remember a discussion of this in the ACS Chemical and Engineering news.. back page.
I don't recall the details It'll take a bit to dig out some of the issues. The discussion happened in the last year or two. I'm thinking there was a corrolation of a person's health and ring marks.

I did a little poking around but haven't found any authoritative answers yet.
The causes I have read so far:
1) cosmetics containing hard materials rub off some of the gold alloy.
2) acidity on a persons skin.
3) anemia

I haven't been able to find any of these properly explaned, but I will keep digging. Many of the people who blame it on their anemia also note that their doctors have said they don't know why anemia would cause it.

I'll keep digging, but hopefully Peteeo will find that C&E News issue. I'll look too but I don't have my own subscription (bad chemist!)

Aside: There's another quick test. Turn down a lower eyelid. It the mucous membranes look pale, you're probably anemic. If in doubt, compare mucosa with those of other people. Riding a bus would give access to a pretty good random sample.

fuse, I found this post on another site
regarding the same issue:

I believe there is truth in the test you are speaking of. Just because I'm severe anemic and it comes up on my skin really dark. Only I rub the gold ring across the inside of my wrist right below my hand. I was told the darker the line shows up means the more anemic you are. I have been told that my whole life and it seems to work everytime its been tested out. I beleive it may have something to do with the type of metal that is in Gold rings themselves that reacts to your body and skin having a low level of iron. But i'm not a dr. jsut a home health nurse. But I have seen it done many times by many differant people.