Like all medicines, aspirin isn't always good. It has side effects that you and your doctor don't want. For example, aspirin can help pain and swelling if you hit your finger with a hammer but its effects also can slow the wound's ability to clot and stop bleeding. Aspirin also can be upsetting to the stomach, especially at high doses often used to treat arthritis.
Research suggests that aspirin given to kids with chicken pox, flu or other viral sicknesses may cause a problem called Reye syndrome, which is potentially deadly.
Aspirin also can cause some people to have trouble breathing (although this is rare), can change the way your kidneys make urine, and can be dangerous at very high doses.
Chemists, therefore, have found other chemicals that have some of aspirin's good effects and lack some of its bad effects. These chemicals are closely related to aspirin. Ibuprofen and naproxen (or Motrin and Naprosyn, respectively) treat pain, swelling and fever like aspirin does. Still, they seem to have a lesser effect on platelets than aspirin. These medicines are called non-steroidal antiinflammatory drugs (NSAIDs). They decrease swelling but aren't steroids (the most potent antiinflammatory chemicals we have). Another in the group of medicines related to aspirin is acetaminophen (or Tylenol). Acetaminophen decreases fevers and pain, but doesn't affect swelling or your stomach as much as NSAIDs do.