Chronic inflammation is believed to be among the leading drivers of many diseases, including heart disease, cancer, metabolic syndrome, diabetes, and arthritis. Some speculate that olive oil’s ability to fight inflammation is behind its many health benefits. Oleic acid, the most prominent fatty acid in olive oil, has been found to reduce inflammatory markers like C-reactive protein. However, the oil’s main anti-inflammatory effects seem to be due to its antioxidants, primarily oleocanthal, which has been shown to work like ibuprofen, a popular anti-inflammatory drug 

Researchers estimate that the amount of oleocanthal in 50 ml (about 3.4 tablespoons) of extra virgin olive oil exerts effects similar to those of 10% of the adult ibuprofen dosage for pain relief. Also, one study showed that substances in olive oil can reduce the expression of genes and proteins that mediate inflammation. Keep in mind that chronic, low-level inflammation is usually fairly mild, and it takes years or decades for it to do damage. Using extra virgin olive oil may help prevent this from happening, leading to a reduced risk of various inflammatory diseases, especially heart disease.

Source: https://www.healthline.com/nutrition/extra-virgin-olive-oil#anti--inflammatory-effects