Hi
If you are highly allergic to nickel, then is certainly possible that your band and/or your Apple Watch may cause a skin reaction.
Note that, band materials aside, there is no model of Apple Watch that has no metal or nickel touching the skin; the magnets in all models of Apple Watch contain some nickel.
If you experience redness, swelling, itchiness or any other irritation or discomfort on your skin around or beneath your watch or band, then Apple recommends that you remove your Apple Watch and consult a doctor / physician before wearing it again.
More information - including about the material content of bands and cases - and related tips from Apple:
- Cleaning your Apple Watch - Apple Support
Includes "Tips to avoid skin irritation, or if you have allergies or skin sensitivities".
- Wearing your Apple Watch - Apple Support
- See under "Skin Sensitivities":
If you are concerned that your band or Apple Watch may have a manufacturing defect, then I suggest that you contact Apple Support (remote diagnostics and/or mail-in service may be available, if required), make a Genius Bar reservation or visit an Apple Authorised Service Provider for assistance:
(Note that you are not talking to Apple here - this is a user-based technical support community).