In 1897, Bayer chemist Felix Hoffmann synthesized acetylsalicylic acid to create a more tolerable, less stomach-irritating form of salicylic acid.

The most significant side effect is an increased risk of gastrointestinal (stomach) bleeding or hemorrhages.

The story of aspirin began millennia ago, as ancient cultures (including Sumerians and Egyptians) used willow bark—which contains salicin—to treat pain and fevers.

Unlike other NSAIDs like ibuprofen, aspirin permanently disables the COX enzyme for the life of the platelet (about 8–10 days).

Commercialized in 1899, it quickly became a staple in medicine cabinets,, eventually helping millions manage aches and reduce fevers during the 1918 Spanish flu pandemic.

By blocking thromboxane A2 production, aspirin prevents blood platelets from aggregating, which is why it is used to prevent heart attacks and strokes.