Watches have a rating system. Jewelry does not — which means "waterproof" on a jewelry page is whatever the brand decided it means. Here is how to work out what you are actually being told.

Three kinds of water, three different attacks. Chlorine, salt and sweat each damage jewelry in their own way — and the metal that shrugs off one is not always the metal that shrugs off another.

Solid gold, gold-filled, vermeil and gold-plated are four different things with four different lifespans, and in the US they are legally defined terms. Here is what each one means and what it buys you.

The honest answer is: for the first several weeks, whatever your piercer put in. Here is why changing early is the mistake people regret, how to know when a lobe is ready, and what to change into when it is.

"Surgical steel" has no fixed definition — several very different grades are sold under it, including some chosen for hardness rather than for sitting in a piercing. Here is what the grades mean and which number to look for.

If earrings make your lobes red and itchy a day later, it is almost certainly nickel. Here is how to tell it apart from ordinary piercing irritation, and how to decode the eight phrases a product page might use for metal.

Green skin is copper — not nickel, and not an allergy. Here is which metals do it, why plating only delays it, and why "what is it plated over" is a better question than "is it gold."

Hypoallergenic is not a regulated word — no US agency defines it for jewelry and nobody has to prove anything before printing it on a box. Here is what it actually points at, why the answer almost always comes down to nickel, and the four things to check on any product page.

Yes — if the earring is steel and carries a water rating. No if it is acetate, and not while a piercing is still healing. Here is what makes the difference, and what the rating does and does not cover.