The question in the title and another: why do cats lick their wounds? are linked. Cats and dogs lick their wounds because it helps to alleviate pain in my opinion. I’ve seen a fox with a badly injured paw constantly lick it and that can only be because it alleviated the pain. The second reason would be that it helped to heal the injury.
The Wikipedia authors have listed an extensive range of benefits to cats and dogs licking injuries because their saliva contains various substances including antibodies, growth factors, nitrates, nitric oxide, an analgesic, opiorphin, and various antivirals including thrombospondin. That is far from a comprehensive list so please visit the Wikipedia website if you wish. The point is that saliva has healing properties.
However, it also contains bacteria and you will see websites almost shouting at their readers that the bacteria in the mouth of a cat is very dangerous. Anybody who has been bitten badly by a cat can testify to this if the bite becomes infected with that bacteria.
There appears, therefore, to be competing effects from a wound being licked by a cat: there are benefits and detriments, there are upsides and downsides. And it is natural for a cat or dog to lick a wound. This naturalness points to nature’s way of animals healing themselves. Clearly wild animals do not have access to a veterinarian. All they can do is lick their wounds and let the body and sunlight do the healing.
Therefore there is some sense in allowing a cat to lick an injury. However, veterinarians will categorically state that they shouldn’t and they will provide an Elizabethan collar or some other device to stop them doing so. Clearly, veterinarians think that the potential health problems that arise from licking a wound outstrip the potential benefits. They disagree with the natural approach. It’s understandable. A lot has been written about the bacteria in a cat’s mouth leading to the conclusion that it should be avoided at all costs.
I think the dangers have been exaggerated. Does human saliva contain bacteria which is less dangerous? I don’t think it does. Wounds in the mouth heal faster than comparable wounds of skin and bone because they are surrounded by the healing properties in saliva. Saliva of humans is also both beneficial and detrimental. The website Science Daily reports on a study in which scientists identified a compound in human saliva that greatly speeds wound healing. They are referring to a small protein called histatin. The point of discussing human saliva is that it demonstrates that saliva can be beneficial to wound healing. I don’t think people should outright reject the idea that cats should lick their wounds. It is a balanced situation upon which veterinarians make a decision.
Please discuss in a comment.