For more than 100 years, aspirin has been used to treat numerous ailments, including mild to moderate pain. This drug reduces inflammation, fever, redness, swelling and discomfort caused by medical disorders such as headaches, infections and arthritis. Aspirin also helps prevent blood from clotting, and has been shown to reduce the risk of heart attacks and strokes.

Aspirin is another name for acetylsalicylic acid. Salicylate is a naturally occurring substance found in the bark of willow trees that was used for hundreds of years as a way to relieve pain. Aspirin was introduced to the U.S. market in 1899. It belongs to a class of medications known as nonsteroidal anti–inflammatory drugs (NSAIDs).

Scientists are not exactly sure how aspirin works. However, they know it prevents pain by acting on the hypothalamus (part of the brain that regulates body temperature, metabolic processes and other autonomic activities) and blocking the generation of pain impulses. It also reduces inflammation by inhibiting prostaglandin production. Prostaglandins are hormone–like substances in the body that help regulate a wide range of physiological functions.

Today, aspirin remains one of the most popular drugs worldwide for treating cases of mild to moderate pain. It is available in tablets (regular, coated, extended–release, chewable and effervescent dissolved in liquid), capsules, gums and suppositories. It is usually taken in an over–the–counter formulation but is also available in prescription strength. People sometimes assume that nonprescription drugs do not have significant risks, but side effects of aspirin can include gastric bleeding and kidney damage.

Recent research suggests that taking aspirin or other NSAIDs around the time of a vaccine might reduce the shot’s effectiveness. Patients may wish to consult their physician about whether to suspend use of aspirin when getting a vaccination.