Is it sanitary for multiple people to use the same Whisper?

Yes, it's sanitary for multiple people to use the same Whisper.

Whisper is designed to always be clean and hygienic. Whisper automatically rinses itself before and after the water is activated. Additionally, Whisper is angled safely out of the way, protected by a full-length nozzle guard, and the auto-retracting nozzle only lowers into position when the water is activated keeping things untouched and sanitary.