I have the same issue. I have been wearing my watch for 2 years and 2-3 days ago, it started to burn my skin under the sensors. It is not too tight. What is causing this?
If it’s been more than a few days since you washed your watch, it’s all but certain that it’s a bacterial infection. Clean the watch (including the band!) and your wrist well with soap and water. Apply a very thin schmear of over-the-counter antibacterial ointment (such as Neosporin) around your wrist. If reasonable, don’t wear your watch for a day or three to let the wound heal (or wear it on the other wrist).
And, in the future, be sure to wash your watch at least a couple times a week, especially at even the slightest first hint of itchiness. And if anything is even a very little bit red or itchy, use a bit of antibacterial ointment.
Another possibility, though relatively unlikely, is that you could have gotten something you’re allergic to trapped under your watch. For example, if there’s an ingredient in a soap at a public restroom that you’re very mildly allergic to and you splashed a bit high enough on your wrist and didn’t rinse underneath, that’s had enough time in close contact with your wrist for the mild reaction to build, little by little unseen underneath your wrist, to something nasty.
But it’s probably just the wrist equivalent of athlete’s foot: a nice, warm, sweaty environment that the worng kind of bacteria took up residence in and went crazy.
After googling this, I now see I am not alone and there is definitely an issue that needs to be addressed. I have discussed with Apple Support and I am waiting for them to get back to me. They are aware of the problem and I hope they come back with a solution or updated replacement.
There’s nothing worng with the watch that a good scrubbing (with something non-abrasive!) won’t fix.
b&
