We wouldn’t recommend sharing with a house guest, but sharing with anyone you kiss should be perfectly sanitary. Simply wash the bar with water first. This allows you to rinse off any germs or dirt that may be on the bar prior to use. The same goes for any bar of soap, simply rinse, then enjoy!
If you or your Tooth Suds partner have a highly contagious disease or your doctor has recommended not to share any hygiene products, do not share.
Want to know more about why tooth soap isn’t dirty? Here’s an article that explains it all.