During the 1889–1890 flu pandemic, the Carbolic Smoke Ball Company manufactured a rubber ball filled with carbolic acid meant to be inhaled through the nose. Confident in their product, the company published advertisements claiming a £100 reward would be paid to anyone who contracted influenza after using the ball three times daily for two weeks. To prove sincerity, they deposited £1,000 in the Alliance Bank.
Louisa Carlill bought the device, used it strictly as instructed, and promptly caught the flu. When she claimed her reward, the company dismissed the advertisement as mere 'puffery' intended to grab attention. The Court of Appeal unanimously ruled in favor of Mrs.
Carlill, establishing that an advertisement targeting the general public can constitute a binding unilateral contract if clear performance terms and intent—evidenced by the bank deposit—are present. The case remains a cornerstone of contract law worldwide.