Hi Gaby
The care instructions for Apple Watch band include:
"Clean Apple Watch if it comes in contact with anything that may cause stains, or other damage, such as dirt or sand, makeup, ink, soap, detergent, acids or acidic foods, or comes in contact with liquids other than fresh water, including those that may lead to skin irritation such as: sweat, salt water, soapy water, pool water, perfume, insect repellent, lotions, sunscreen, oil, adhesive remover, hair dye, or solvents."
Avoid using lotions (some moisturising lotions, for example, are acidic) or any other potentially damaging agents in areas of the wrist where the watch is worn and to generally keep the watch and band clean and dry.
Apple also advises that you should not use soaps, cleaning products or abrasive materials on your Apple Watch (including polishing or buffing it with abrasives).