Hydroxytyrosol is a polyphenol found in olives and olive leaves resulting from the hydrolysis of oleuropein with potent antioxidant and anti-inflammatory activities. Hydroxytyrosol has been found to increase the activity of the oxidative defense enzyme, manganese superoxide dismutase (MnSOD), and to extend the chronological lifespan of skin cells. Hydroxytyrosol also turns on the transcription factor FOX03a. Treatment of keratinocytes with hydroxytyrosol has resulted in the upregulation of numerous antioxidant proteins including heme oxygenase-1 (HO-1), glutaredoxin, and glutathione. Evidence also suggests that hydroxytyrosol exhibits protective activity against vascular disease, cancer, and diabetes. Furthermore, evidence indicates that hydroxytyrosol strengthens the immune system.