You Want to Spit on My Wound?

I know it is April, but this is not an April Fool’s joke. Could it be that saliva might have some useful healing properties? It is well known that oral wounds heal faster and with less scarring than skin wounds despite existing in an environment filled with all kinds of bacteria.¹ We know animals treat their wounds by licking them with reasonably good results. Believe it or not, there are reported instances of people letting dogs lick human wounds to improve healing!² Whenever we hear about these instances, we generally disregard them as being ridiculous and nasty, but could it be that saliva might be a good wound care treatment?

In 2015, Dr. Ole Sørensen and his colleagues investigated the reasons wounds of the oral mucosa healed faster than those of the skin.³ They were culturing skin cells, wounding them, and treating them with different products to determine the healing of the injured cultures. When it came to testing saliva, the team apparently looked at each other with questioning looks, and then Dr. Sørensen spat into the tissue culture dish! Amazingly, the wounded cells in the tissue culture healed faster than other healing products tested.³ Because of this and other works, it has been shown that saliva may not be a bad choice to treat a wound of the skin.

One of the properties that make saliva a good choice for treating skin wounds is that it has an analgesic effect for painful wounds. Opiorphin, a peptide with an analgesic effect, has been found in human saliva.⁴ In animal studies, Verrier² reported that 1 mg of opiorphin has the pain relieving equivalency of 3 mg of morphine. Another benefit of saliva is that it promotes blood clotting, which was initially studied as early as the 1920s, and adding small amounts of saliva to human blood caused rapid clotting.⁵

The antimicrobial effect of saliva is well known due to several proteins and peptides that act against bacteria to reduce the chance of infection.² Salivary nitrite dissociates into nitric oxide in the saliva-treated wound and further attacks the local bacteria.⁶ Likewise, numerous growth factors and anti-inflammatory molecules that aid healing have been identified in saliva.² One particular peptide, histatin-1 (one of several histidine-containing peptides) has recently been identified in human saliva.⁷ In addition to providing antimicrobial and anti-inflammatory effects, it can stimulate epithelial and fibroblast migration and promote angiogenesis.^2,7

From the aforementioned literature, it appears we may have been wrong about licking our wounds. Since all of these beneficial effects of wound healing with saliva have been identified, doesn’t it seem logical that we should begin a clinical trial using it in the treatment of human wounds? There are a few important questions we need to answer up front: Who provides the saliva? Does the doctor or nurse just spit on the wound as part of the treatment? Does the patient supply the saliva for their own wound? How much saliva is needed per treatment? I have a feeling that recruiting patients for this trial will not be easy no matter who provides the saliva! Even so, it appears that research in this area should move forward. There may be beneficial effects to utilizing the composition of saliva in the treatment of chronic wounds. Hopefully, these treatments will be made in the laboratory, but if not, does anyone out there want to volunteer to be a saliva donor?