Answer: Unflavored: no (Star-K, cRc).
Reason: Floss fibers and wax are innocuous, but flavors are kosher-sensitive.
Source:
- Star-K: its list of products that need no hechsher includes dental floss.
- cRc: the fibers and wax in dental floss do not require kosher certification, but many varieties are flavored, and flavors are kosher-sensitive; unflavored is preferable year-round and required for Pesach.
Related questions:
- Does toothpaste need a hechsher? No.
- Does mouthwash need a hechsher? No (cRc), though a kosher variety is preferred.
References: Star-K, “Approved Without A Hechsher” list · cRc (askcrc.org), “Dental Floss (Policy)”
