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Why does gold darken some women's skin?

Our AP chem class was discussing the fact that if 14k gold touches some women's skin, it will turn the skin grey or black. This generally only works on women, and is said to be a sign of iron deficiency. It is also most noticeable on the face. However, we were able to find no chemical explanation for this. If you can help, I would love any information you can give me.
Margie Dickerson

Margie,

I don't know what's causing the color change. If there really is some connection between the darkening and iron deficiency, such a noticeable symptom would be familiar to diagnosticians. You might ask a doctor about this.

Gold is chemically rather inert. One of the other metals present (silver, nickel, copper) in the jewelry is probably causing the color change. Skin reactions to gold do exist. But they involve gold salts, not the metal, and the reactions are described as contact dermatitis, not as dark spots.

Gold is a soft metal, and it probably wears off the surface of the jewelry a bit faster than the other metals. If the jewelry is just gold-plated, the plating may be wearing away and allowing the base metal or plastic to contact the skin directly. It may be the base material that's causing the darkening.

Nickel causes most of the skin problems with jewelry. But as with gold allergies, nickel hypersensitivity seems to be a burning rash, not a darkening of the skin.

Some electrolysis of the metals in the jewelry will occur on the moist, salty surface of the skin. This definitely happens with copper; its ions stain the skin green. In fact, copper rings were once worn as 'blood purifiers'- the green discoloration was thought to be impurities drawn from the blood. If silver in the jewelry is oxidized on the chloride-rich surface of the skin, light-sensitive silver chloride might be formed. The AgCl will photoreduce to black silver crystals on the skin. Or, you could be getting an oxide or sulfide of one of the metals; many of those are black.

I suspect that the real story involves more than just simple metal redox reactions on the skin.

Reader Comments

Hi. Great site. I just read your answer to the question about why some women's skin turns dark when gold is rubbed on it. You may not have much experience with the mysteries of cosmetics, so I just wanted to let you know that it's the "foundation" or "base" that turns dark, not the woman's actual skin. Way back in high school, girls used to sneak up on each other and streak a ring on a face to test if someone was wearing make-up.
Kate Petersen, 3/01/00

I do not wear any makeup/foundation etc on my hands and in the winter more so than in the summer my fingers turn very dark from my gold jewelry. So, I do not think it is from foundation.
anonymously contributed, 10/08/00

I have repeatedly tried rubbing my gold ring on my hands (no makeup) and also my cheek with zero makeup, and it always leaves black streaks. Some of my friends' skin in the same places leaves no marks whatsoever. Some mark very easily and darkly. Weird! I had heard long ago that this signified and iron deficiency, but perhaps this is a myth. The rings I used to try it are all 10 or 14 karat.
Jen Hughes, 10/18/00
.

I recently bought my girlfriend a diamond with a 14kt gold ring. One reason that gold can make skin darker is because of certain types of makeup. One day she just took the ring off and made a line on her face with it. I couldn't believe it. I guess that is a way to tell if it is real gold also.
anonymously contributed, 11/15/00

Author: Fred Senese senese@antoine.frostburg.edu



General Chemistry Online! Why does gold darken some women's skin?

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Last Revised 02/15/10.URL: http://antoine.frostburg.edu/chem/senese/101/misc/faq/gold-spots.shtml