Both playing a role in the pharmaceutical industry, acetylsalicylic acid and hydroquinone are pictured here in a colorful crystal medley. Known by millions as aspirin, acetylsalicylic acid has been effective in the over-the-counter treatment of arthritis, headaches, cold and flu symptoms, and most recently, as a prophylactic fighting stroke and heart attacks. Originally extracted by the ancient Greeks in a related derivative from willows, biochemists at the Bayer Corporation synthesized and marketed acetylsalicylic acid and added a buffered outer layer to protect sensitive throat and stomach linings from irritation and potential hemorrhage. Hydroquinone, in contrast, has much more limited use in pharmaceuticals and cosmetics, and is potentially a carcinogen. It has been detected in analyses of second-hand cigarette smoke and is known to be a skin and respiratory irritant.