 A protease inhibitor, secretory leukocyte protease inhibitor, is present in saliva and is both antibacterial and antiviral, and a promoter of wound healing.Nitrates that are naturally found in saliva break down into nitric oxide on contact with skin, which will inhibit bacterial growth.Saliva contains growth factors such as epidermal growth factor, VEGF, TGF-β1, leptin, IGF-I, lysophosphatidic acid, hyaluronan and NGF, which all promote healing, although levels of EGF and NGF in humans are much lower than those in rats.