I would bet that almost nobody washes their hands or face after their cat licks them. I don’t. But a science journalist, Erika Engelhaupt, writing for National Geographic recommends it because of the hundreds of different species of bacteria in the mouths of cats and dogs which are alien to humans. One bacteria species, in cat and dog saliva, Capnocytophaga canimorsus, can be deadly but very rarely.
Up to half of cat bites become infected and sometimes people end up in hospital but often this is due to human carelessness, ignorance and neglect. Dogs sometimes lick a person’s hand or foot where there might be an injury allowing the bacteria to enter the bloodstream – bacteremia. Humans have lots of bacteria in their saliva as well but 85% of it is of a different type. Therefore we are not immune to the bacteria in the mouth of cats and dogs.
There are around 400 kinds of oral bacteria in dogs. In cats there are almost 200 different types of bacteria. About 50% of the bacteria in cats is the same as that in dogs. When a cat grooms himself he covers himself in his oral bacteria. In one study it was found that nearly 1 million living bacteria were present on each gram of cat hair. How much of this bacteria is transferred to a person’s hand when she strokes her cat? Apparently, relatively few: around 150 or so bacteria made the transfer. Also, most of the cat’s oral bacteria won’t survive indefinitely on the cat’s coat. This shouldn’t be a problem but some experts advise us to wash our hands even after we pet our cats.
I would certainly wash my hand if a strange cat bit it and I’d probably disinfect the area as well. I don’t wash my hand when my cat licks it. Perhaps the real danger lies in having a break in the skin where the cat licks then there could be a transfer of the bacteria into the bloodstream. Stricter precautions might apply more to elderly people and babies who, in general, have weaker immune systems.
At one stage it was thought that a dog’s saliva had a curative and sterilising effect. The saliva does contain substances which can sterilise but it appears that the bacteria outweighs the beneficial effects in relation to humans.
There have been some gruesome stories of people suffering incredible injuries because their dog licked them. In one case a woman, Julie McKenna, was licked on her foot by her dog. She had suffered a burn on the foot earlier. The dog’s bacteria entered her bloodstream through the burn and she turned purple and eventually part of her arms and legs turned black. She survived with antibiotics in hospital but she lost part of her foot, part of her arm and all her fingers and toes. It was a completely life changing event.
It is a question of common sense. And prevention, as usual, is better than a cure. Don’t get bitten and watch out for licks on open wounds.