Very important. Handwashing gets its own method and a set time, which most steps in wound care don’t.
Here’s the method. Take all jewelry off your hands. Wet your hands, pointing them downward under warm running water. Add soap and wash your hands for 15 to 30 seconds, cleaning under your nails too. Rinse well. Dry with a clean towel. An alcohol-based cleanser is the alternative.
For timing, a memory aid works better than counting: sing Happy Birthday or the Alphabet Song one time through.
When you wash during a dressing change matters as much as how, and this is the part people most often rush. You need clean hands before touching the dressing, again after the old dressing is removed, and again when the new dressing is on. For wet-to-dry dressings, wash your hands thoroughly with soap and warm water before and after each dressing change, and between every stage.
Setting up the space is part of the same idea. Make sure you have all the supplies you need handy, and have a clean work surface. Hands washed and then used to hunt for scissors in a drawer are hands that have been washed for nothing.
Two related instructions: do not touch the inside of the dressing, and use a dressing only once. Never reuse it.
The reason for all of this is simple. Your skin protects your body from germs. When the skin is broken, even during surgery, germs can enter and cause infection.