I can't edit my previous post, but I talked with Garmin over the phone and they're sending me a different watch. The lady said the plating on my watch's underside is not nickel, but some kind of fibrous polymer (whatever that means in terms of allergies?). But whatever it is, I'm apparently allergic to it because my arm is still itchy and throbbing. All I have to do now is send the watch in and they're upgrading me to a different one that's $50 more.

If this new watch does the same thing, I'll just go back to a Fitbit. I doubt there is much we can do about the Garmin watches if I get irritated again. But man, what a freaking weird allergy.