It happened to me as well when using silicon wrap intensively.
Try to use different material that allows your wrist to breathe. I'm not sure that it is allergy, more like the fact the wrist skin cannot breathe thru silicon.
Me too, on the Galaxy Fit I got in the summer, it's been developing for the last few weeks, I'll be contacting Samsung this week. It seems to be a common issue?!
The Gear Fit I had at the beginning of the year was fine.
Saying not to get it wet or remove it often defeats the object of having a device which monitors your activity, analyses your sleep and is sold as waterproof!!