In February 1917, Bayer lost its American patent on aspirin, opening a lucrative drug market to many manufacturers. Bayer fought back with copious advertising, celebrating the brand’s purity just as the epidemic was reaching its peak.

Aspirin packages were produced containing no warnings about toxicity and few instructions about use. In the fall of 1918, facing a widespread deadly disease with no known cure, the surgeon general and the United States Navy recommended aspirin as a symptomatic treatment, and the military bought large quantities of the drug.

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