According to study from Northwestern University, many people don't pay attention to the drugs' ingredients.
The authors found that only 31 percent of those interviewed knew that Tylenol contained acetaminophen. Only 19 percent knew Advil contained ibuprofen.
When used properly, these active ingredients can be safe but too much can do damage. For example acetaminophen is in more than 600 different medicines.
Researchers suggest that lack of awareness could be the main reason why acetaminophen overdose is a leading cause of acute liver failure. Details are in the American Journal of Preventive Medicine.