Of Nickel and Niobium

I love it when something I’d usually think was totally stupid and mundane becomes an opportunity to learn science.

A few weeks ago, I had the pleasure of being maid of honor in a best friend’s wedding. When it came time to decide on the bridal party’s jewelry, we ran into trouble — I’m terribly allergic to most metal things, and therefore haven’t worn earrings in nearly a year. My piercing holes don’t want visitors. They’re closed for business.

But I really, really like my friend, and I didn’t want to be the reason her wedding wasn’t absolutely perfect, so I took one for the team. I brought a needle and some Neosporin over to a well-lit mirror. You can imagine the rest.

It worked out fine, and all of her bridesmaids had earrings. Hooray! (I also didn’t get an infected earlobe. Double hooray!) In the interim, though, we got to talking. My friend is pretty crafty, and incidentally makes her own jewelry. We discussed various metals that might get around my inability to wear earrings, which until that moment I had always assumed was un-fixable. When I got back, I researched it further, and what I found out was pretty interesting.

Let’s begin!

WHAT MAKES A GOOD JEWELRY METAL?

Well, it can’t be toxic. So arsenic and mercury are right out. You also don’t want it to be something that many people are allergic to. And besides that, you want it to be pretty and hold up to wear and tear — that means it shouldn’t discolor or break very easily.

When I complain of my allergy, the answer many people bring to me is gold. Nobody’s allergic to gold; hardly anybody, at least. The problem lies in the fact that you can’t make jewelry out of pure gold. Pure gold is soft. If you tried to forge it into a ring or a necklace or earrings, it would hold together about as well as silly putty. There’s your breakage element.

When one metal poses a problem like this, metallurgists combine it with other metals that possess the quality they’re looking for — in this case, strength. This creates an alloy. More often than not, gold is mixed with copper and zinc and/or layered over a harder metal to produce a lustrous, durable piece fit for an earlobe or collarbone. Gold can also be mixed with other metals to produce various hues, including the nickel and platinum used to create white gold and the copper used to form rose gold.

This can make it tricky for someone like me to know exactly what metal I’m allergic to — is it the base element itself, or is it some unlabeled metal that was used to create its alloy?

OTHER ALLOYS

The alloy mystery continues when you get to other jewelry metals. Surgical steel contains chromium to stave off corrosion, molybdenum to ensure strength, and nickel to add a pretty finish. Sterling silver is usually mixed with copper, which makes it stronger than fine silver but also causes it to tarnish more easily. There’s also a version called nickel silver, which doesn’t actually have any silver at all: it’s an alloy of nickel, zinc, and copper. (Thanks a lot, jewelry makers.)

WHICH METALS CAUSE THE MOST ALLERGIC REACTIONS?

I’m gonna cut to the chase: Nickel. Nickel causes allergic reactions. Sure, there are small percentages of people who are allergic to less common alloying agents such as chromium, cobalt, and palladium, and even fewer still who are allergic to precious metals like pure gold. But nickel is far and away the most likely candidate when a person breaks out in a rash from wearing jewelry.

About 10% of people living in the industrialized world have a nickel allergy — contact dermatitis, to be precise. Nickel is a wily element: when exposed to moisture (like sweat), it tends to dissolve and form tiny crystals, which hang out on the skin until a sensitive body fights back.

THE BIOLOGY OF NICKEL SENSITIVITIY

The exact reason for nickel allergies isn’t entirely understood, mostly because they don’t happen in animal trials. Lab mice aren’t allergic to nickel. This led to a pretty cool theory, though: some German researchers at the Institute of Experimental Dermatology in Münster realized that this is all because our immune receptors are just a little bit different.

It all comes down to a receptor called TLR4, the body’s first line of defense against invaders. It essentially blows a whistle and calls T cells to the area to wipe out anything that shouldn’t be there. This process leads to inflammation, rashes, itching, and tenderness — the classic signs of a contact allergy. TLR4s take a while to show up, though, so most allergic reactions on the take 24–48 hours to develop. Strangely, nickel only takes 24 hours to do damage — not nearly enough time for TLR4 to finish its business.

These researchers found that nickel is essentially being its own T-cell recruiter; its own whistleblower. Mice have the same TLR4 receptor, but don’t have any reaction when nickel is introduced on the skin. They discovered that a single amino acid called histidine appears at a different place on the receptor in mice than in humans. When they tweaked mice so that histidine was expressed in the same place, bam. Nickel allergy.

SO WHAT’S THE SOLUTION?

Make-believe T-cells are cool, but what’s cooler is that us nickel-allergic folks (and the jewelry designers who love us!) can explore brave new worlds of the periodic table for our jewelry choices. Obviously, if it can be proven than a gold or silver piece contains no nickel (and you’re not a big fat cheapskate like me), it’s probably safe. But there are other elements that work even better.

Titanium, when in its purest form, is physiologically inert. This means that it doesn’t react with the body at all, a trait that only a handful of jewelry metals share. The bad news is that it comes in a wide variety of alloys, some of which contain nickel. It can also get a little pricey.

There’s also niobium–a metal mostly used in jet engines, steel pipelines, and superconductors. It too is physiologically inert, but its strength and rust resistance make mixing it with other metals unnecessary. Because it can be anodized into a nearly unlimited number of colors (including faux copper, silver, and gold), it’s easy to work with, and it’s relatively cheap, I’m surprised more jewelry makers don’t use it.

So I ordered myself some niobium studs. They’re doing quite well — they don’t hurt or make my ears swell up. With a little research, I found out that my all-encompassing, “woe is me” sensitivity to every metal ever created is really just a simple nickel allergy, the same one that 1 in 10 people living in the Western world suffer from.

Therefore, jewelry artists, don’t take it as self-serving — just take it as a way to add the missing 10% of the population to your customer list — when I leave you with this plea.

Think about niobium.

Gold image by Striving to a goal, nickle image by flickr user jasonbolonski, other images by moi. Also, a ton of thanks to fellow ‘Labber Ryan, whose scientific and metalworking expertise did wonders for my research.