All watch bands will get dirty over time. Dust, food, sweat, lotions, and more can affect the look of your watch band. How often a band needs to be cleaned will depend on your situation. We recommend cleaning as necessary, but at least once every 2 weeks.
Generally speaking, most Apple Watch bands can be cleaned using a lightly moistened cloth. How much water and/or soap can be used will largely depend on the material that the watch band is made of:
Silicone: Silicone bands are water proof, so can be washed with warm water and hand soap. Avoid harsh cleaning agents as that may degrade the protective coating around the band.
Leather: A common misconception, leather is actually not water proof. Leather will absorb water and either deform or lose its color. When wet leather dries, it will almost certainly crack. For that reason, never submerge leather bands under water (not even running water). If it gets wet (such as from rain), water should be wiped off immediately. We recommend wiping down leather with a dry cloth, or if absolutely required, a very lightly moistened cloth (and then dried immediately).
Nylon: Nylon bands (that are made of only nylon) should be able to cleaned with a moistened cloth. Be aware that nylon tends to absorb water so needs to be thoroughly dried (otherwise it will start to smell if the water stays inside the material). For this reason, while it can be cleaned under running water or even a washing machine, we do not recommend doing so unless you can't get it cleaned in any other manner.
Stainless Steel: Metal bands (including Milanese) made of 316L stainless steel can be washed with warm water and hand soap. Avoid harsh cleaning agents as that may degrade the protective coating around the band, and affect the color of the band. Be careful when using excess water (such as washing it under running water) because the design of those types of bands will often trap water in crevices.
Wood: Wooden bands, like leather bands, should not be washed. Wood (with varnish) is a little more tolerant of water, so you can wipe it down with a lightly moistened cloth (and then dried immediately). Prolonged exposure to water will usually result in the deformation and/or cracking of the wood.
What about the adapter and buckles? If they are made of stainless steel, then they can be cleaned with a moist cloth or even running water (if the material of the band allows that).
What about hybrid bands (made with 2 different material)? To avoid damaging your band, clean the band like you were cleaning the most sensitive material. Take for example a band made with nylon and leather. Because leather is the more sensitive material, clean the band like you would a leather band.
After cleaning your band, we recommend you dry it thoroughly. If you didn't use a lot of water, you won't need to spend a lot of time drying. If you washed it under running water, more care must be taken to get water out of crevices and other hard to reach places. Generally, we recommend using a paper-towel to soak up any water or moisture. If you suspect water has been trapped in an area that you cannot reach with a paper-towel, then you can use a hair-dryer (with zero heat... just blow out room-temperature air).
In full transparency, these tips are for the Apple Watch bands we sell. If you purchased your band from anyone else, your band may require different care (not all watch bands are created equal).
Cleaning and other tips, specific to each of our watch bands can be found in our Owners Guides section.