My Apple Watch has irritated my skin.

See here for the guidance and materials being used, etc:

Wearing your Apple Watch - Apple Support

Note also this advice there:

If you experience redness, swelling, itchiness, or any other irritation, you may want to consult your physician before you put your Apple Watch back on.

Contacting Apple Support is also recommended in that situation.

Thank you for participating in the Apple Support Communities.

We want to make sure you reach the right team for help with your device. We recommend that you contact Apple Support directly. Depending on your region, you may be able to reach them here: Get Support.