Allergies

Yes. https://support.apple.com/en-us/HT204665

I didn’t know I had a nickel allergy, but I bought an Apple Watch 5 and had a severe reaction to the back of the watch and the fastening stud in the sports band. I contacted Apple Support, but all they offered was that I see a dermatologist and take it back to where I bought it and sent me the article on ‘wearing the watch’ that I had already told them I had seen, tried all the steps in it, and that was why I was contacting them. It is a great bit of kit - but steer well clear if you have an allergy to the compound (used in both series 4 and 5).