Listerine is a brand of antiseptic

Antiseptic

Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction...

 mouthwash

Mouthwash

Mouthwash or mouth rinse is a product used to enhance oral hygiene. Some manufacturers of mouthwash claim that antiseptic and anti-plaque mouth rinse kill the bacterial plaque causing cavities, gingivitis, and bad breath. Anti-cavity mouth rinse uses fluoride to protect against tooth decay...

. Its original formula has a notoriously strong flavour, although variations have been released that are marketed as tasting milder. The product is marketed under the slogan "Kills germ

Microorganism

A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

s that cause bad breath". It was named after Joseph Lister

Joseph Lister, 1st Baron Lister

Joseph Lister, 1st Baron Lister OM, FRS, PC , known as Sir Joseph Lister, Bt., between 1883 and 1897, was a British surgeon and a pioneer of antiseptic surgery, who promoted the idea of sterile surgery while working at the Glasgow Royal Infirmary...

 who promoted the idea of sterile surgery by sterilizing instruments.

Listerine is one of the most popular mouthwashes sold in the United States.