This narrative essay unpacks how Listerine revolutionized marketing by transforming bad breath into the medical condition "halitosis." By tapping into deep-seated social anxieties and using fear-based tactics, Listerine created a new market for mouthwash, reshaped hygiene practices, and set a controversial precedent for psychological advertising. The document explores the campaign’s origins, its cultural and psychological manipulation, its explosive financial success, and the ethical questions that still echo in today’s marketing world.