The human body can make its own salicylic acid

Salicylic acid (SA) is the active product of the breakdown of acetylsalicylic acid (ASA, aspirin).

SA exists in the blood of people who have not recently taken aspirin. Vegetarians had much higher levels, almost matching those in patients taking low doses of aspirin. Based on those findings, the researchers previously concluded that this endogenous SA came from the diet, since SA is a natural substance found in fruits and vegetables.

Now the group reports on studies of changes in SA levels in volunteers who took benzoic acid, a substance also found naturally in fruits and vegetables that the body could potentially use to make SA... The results reported in the study suggest that people do manufacture SA.