It has long been regarded a sign of affection and a form of bonding.

But research suggests kissing your baby on the lips can actually give them cavities.

Finnish scientists warned just a peck, or a smooch, can spread harmful bacteria from parent to baby.

Even sharing spoons can raise the risk of dental problems, as bacteria that causes cavities can be passed on in saliva.

Advertisement

The latest study confirms mounting evidence that stretches back decades to show that kissing babies can damage their teeth.

Researchers at the University of Oulo, led by Jorma Virtanen, published their findings in the journal BioMed Central Oral Health.

READ MORE: • NZ Study: Why kids are encouraged to play with fire, knives, saws in playgrounds

They quizzed 313 mothers about their thoughts on their health knowledge and their behaviours, such as sharing a spoon with their child.

They were also asked about how often they brush their teeth, smoking habits, age and level of education. These can alter someone's risk of cavities.

The scientists were concerned as the results showed 38 per cent of mothers kissed their child on the lips and 14 per cent shared a spoon with their child.

However, 11 per cent were under the belief that oral bacteria cannot be transmitted from mother to child.

They called for further awareness to be given to new parents to advise them on how to avoid sharing bad bacteria with their children.

It comes after an Australian dentist last month re-iterated the widespread warnings over the dangers of giving youngsters a peck.

Dr Michael Chong, who practices on the Gold Coast, stressed parents should get a check-up for any cavities before they do so.

He said that if parents unknowingly have cavities themselves, they risk passing on their damaging oral bacteria to their children.

Dr Chong also suggested parents avoid blowing on their child's food to cool it down. And he said tasting a meal to check the temperature should be avoided.

Other common mummy-hacks to steer clear of include pre-chewing baby's food, and cleaning dummies by sucking on them before handing them to bub, he said.

READ MORE: • Why you might find newborn babies ugly

Kissing a baby on the lips doesn't just raise the risk of oral cavities, however.

A heartbroken couple revealed last summer that their 18-day-old baby daughter died after she contracted herpes through a kiss.

Shane and Nicole Sifrit, from Iowa, said their daughter was infected with meningitis HSV-1, which is caused by the herpes virus, also responsible for cold sores.

Why does kissing lead to teeth rot in children?

Parents often kiss their children to show signs of affection but one dentist claimed in February that doing so runs a major health risk.

Dr Michael Chong, a pediatric dental specialist from the Gold Coast, said mothers and fathers with active dental decay could risk passing on their bacteria to their children.

"The damaging and non-damaging bacteria is spread through the transfer of saliva, and is most likely to pass to infants around or even before the time of baby teeth erupting," he told The Sunday Mail.