[kale]

Stainless Steel is a huge class of metals, most (but not all) have nickel in them. Also alloys of cupronickel, coin metal, cobalt chromium, and nitinol all have nickel in them. And certain countries lie constantly about nickel content in metal they sell. When we source for medical implants, we have to specify no material from certain countries, because we can't trust their certifications, and we can't re-do all of the certification testing on our own.

Nickel is just too useful (and pre-existing in a lot of metal ores, I think) to stop using it, despite the fact that a large percentage of people are allergic to it.