London - They say a dog is a man’s best friend – but being overly affectionate with your pet could be bad for your health.

Dog owners who kiss their pets – or let them lick their mouths – could catch gum disease from their pets, experts have warned.

This is because exchanging a smooch could cause a harmful swop of dangerous mouth bacteria.

Left untreated, gum disease can turn into periodontitis, an inflammatory disease of the mouth tissue, according to report in the Archives of Oral Biology.

Periodontitis is a severe form of gum disease that affects the tissues that support teeth and hold them in place.

If left untreated, the jaw bone can decay and small spaces can open up between the gum and teeth. The teeth may become loose and eventually fall out.

Most dogs suffer from periodontitis, though only about five percent will develop a cavity.

The warning follows research last year which examined the dental health of dog owners in Japan.

A potentially harmful oral microbe normally found in dogs, but not in humans, was discovered in 16 percent of owners – usually those who had a close-contact relationships with their dogs.

But germs were also passed from master to pet.

The researchers found 10 human periodontitis-related bacteria in their pets. Even low-levels of contact could result in transmission.

However, the risk of cross-contamination may depend on the teeth-cleaning habits of both man and dog, Dr Paul Maza, of the College of Veterinary Medicine at Cornell University, told Fox News.

“Many of the different types of bacteria in dogs and cats are the same type of bacteria as in humans. If owners practise oral hygiene on their pets, such as brushing their teeth, a pet’s mouth can actually be even cleaner than a human mouth.”

He said that although the grooming technique of pets could cause faecal bacteria in the mouth, it was often swallowed and out of the mouth quickly.

People who should think about avoiding a kiss include those with a compromised immune system and the elderly. – Daily Mail