If you must use both to maximally remove infectious organisms from the hands, it's best to wash hands with soap and water, dry, then apply hand sanitizer and allow to air-dry on the skin.
This is because dirt, food, oils, etc. on your hands can make the sanitizers less effective. If you first wash your hands to remove barriers to their effectiveness, the sanitizer will be more useful.
In a non-hospital setting, though, it's unnecessary to wash with soap and water and use a hand sanitizer. For the most part, proper hand washing is as good or better than using hand sanitizers at removing bacteria and viruses from your hands.1
Research has shown that hand sanitizers can be as effective as hand washing only in certain situations.
The major problem is that many people don't take the time to thoroughly wash their hands.
Reasons to use both include:
- coming in close physical contact with persons at high risk for infection (such as newborns, the very old, the ill, or the immunosuppressed)
- having direct physical contact with someone with an upper respiratory infection, skin infection or diarrhea,
- working in settings where infectious diseases are commonly transmitted, such as food preparation, and/or crowded living areas (child-care centers, preschools, prisons, or chronic-care residences), or
- when you're uncertain if the water you're using to wash your hands is drinking-water clean (e.g. after a flood or when you have a "boil water" advisory.
How to wash hands properly: 1. Wet hands with clean, running water (warm or cold), turn off the tap, and apply soap. 2. Lather your hands by rubbing them together with the soap. Be sure to lather the backs of your hands, between your fingers, and under your nails. 3. Scrub your hands for at least 20 seconds. Need a timer? Hum the "Happy Birthday" song from beginning to end twice. 4. Rinse your hands well under clean, running water. 5. If you're using a tap, turn water off with a paper towel. 6. Dry your hands using a clean (new) towel or air dry them.
1 Hand Hygiene and Hand Sanitizers
Wash Your Hands - CDC