Could your dog’s kisses be making you feel older than you are?

Your dog’s sweet habit of licking your face might carry an unseen danger. Behind that affectionate gesture could be a microscopic threat quietly damaging your health. A Queensland researcher discovered it the hard way—inside her own mouth.

Dr Simone Sleep, a dental researcher and biomedical scientist, had battled unexplained fatigue, brain fog, and stubborn gum issues for years before finally uncovering the culprit. The intruder was a parasite called Trichomonas tenax—a microorganism that can hitch a ride from pets to humans.

‘I was not expecting a dog parasite to be running around in my mouth,’ she shared, describing her reaction as ‘absolute shock, horror.’

A parasite that refuses to go quietly

Trichomonas tenax is a protozoan often found in the periodontal microenvironment of the mouth, with research linking it to gum disease. Its name—derived from the Latin word for ‘tenacious’—reflects just how difficult it is to eliminate.

In some regions, more than 50 per cent of the population carried this parasite, particularly in connection with gum infections. Unlike harmless oral bacteria, it actively damaged mammalian cells and released virulent proteins once established.

How pets unknowingly pass it on

The pathway into human mouths was alarmingly simple. The parasite had been identified as zoonotic, meaning it could pass between animals and humans.

Sensitive diagnostic tools confirmed its presence in cats, dogs, and horses—widening the circle of risk for pet owners.

A typical transmission chain began when a dog cleaned itself after toileting, then offered its owner a lick on the face. The ‘kiss’ could transfer parasites directly into the human mouth.

Healthy gums rarely hosted the parasite, which suggested it was not an innocent bystander but a contributor to disease once it appeared.

A hidden danger for seniors

Australians over 60 faced heightened risks from this parasite due to weaker immune systems and common medication effects.

The presence of oral pathogens was linked to pneumonia when inhaled into elderly or immunocompromised lungs. Trichomonas tenax had been identified as a frequent cause of pulmonary infections, sometimes leading to severe complications like pyopneumothorax.

The same symptoms Dr Sleep reported—bleeding gums, fatigue, and low iron levels—were particularly concerning because many seniors assumed these were just signs of ageing.

Why it often goes undetected

Dentists rarely spotted T. tenax during routine check-ups.

Detection required advanced tools like PCR testing, which could identify the parasite in small percentages of dental plaque and saliva samples. Microscopy and culture methods were far less effective.

This meant many Australians might unknowingly carry the parasite for years, enduring unexplained health issues without real answers.

Beyond the mouth—systemic health risks

Research revealed that T. tenax could disrupt gum epithelial cells, destroy cell junctions, and trigger inflammatory responses in gum and lung cell lines.

Dr Sleep warned that bleeding gums were a ‘dead giveaway’, along with trouble maintaining iron levels.

The parasite was known to worsen necrotising ulcerative gingivitis and periodontitis, fuelling further oral and systemic decline.

Staying safe without avoiding pets

Experts emphasised that prevention did not mean giving up on beloved animals.

Instead, breaking the cycle of transmission was key. Dr Sleep suggested teaching pets to offer a ‘high five’ instead of kisses. Owners were advised to avoid close contact immediately after grooming or toileting, maintain strict hand hygiene, and never share food or water bowls.

Australian dental organisations encouraged seniors to attend regular check-ups and to raise the possibility of parasites with their dentists if unexplained symptoms persisted.

A new understanding of oral health

This discovery marked a turning point in recognising the broader health implications of oral parasites.

Researchers stressed the need for more epidemiological studies to clarify the pathogenic role of T. tenax and to develop effective treatments.

For seniors who treasured their pets, the message was not about fear but awareness—by making small changes in daily interactions, it was possible to preserve both health and companionship.

Parasites don’t just hide in our pets—they can also be lurking in the environments we enjoy every day, creating risks that are easy to overlook.

Just like Trichomonas tenax quietly causes health issues in the mouth, other parasites can invade the body in ways that lead to far more serious consequences.

One recent case highlights how a common park parasite can cause permanent damage if left unchecked.

Read more: This terrifying parasite at your local park can blind you–here’s how to protect yourself!

Could a seemingly harmless lick from your pet actually explain some of the health struggles you once thought were just part of ageing?