After 3 months of wearing my new Apple Watch 5, I suddenly got a burning pain on the inside of my wrist just as I was going to sleep the other night (I sleep with it for the sleep data). I tried to touch it and it made it exponentially worse. Even though I was half asleep, I had enough wits to consider it might be my watch band giving me the pain, so I immediately took it off and put on the other wrist. When I woke up, it looked like I had had a blister that popped and was now dry. It was exactly under the metal clasp of the band that came with it.
I wish I could say that Apple replaced my band, but after an hour on the phone with them, and sending them pictures, they sent me an email with a link on how to wear my watch, and how to clean it. I'm not sure if cleaning it would help that much, but I happened to have an appointment with an allergist the next day, so asked her about it. She gave a few suggestions, and since I was having other skin sensitivities, suggested that I get tested for metals, which is not a convenient in & out test. She also agreed that keeping the skin and the metal clean, even if it looks clean, can also help any small particles of dirt or debris from causing irritation.
I am disappointed that Apple wouldn't even suggest other bands to wear, but I will probably buy a different band. I found some on Amazon that some of the reviewers said did not bother their metal allergies which sounded very much like my reaction.
I guess since my reaction wasn't at the watch site, but rather, the band, they didn't feel compelled to do as much, but blad that they took better care of the others who have had a good experience with them.