Are Cats’ Mouths Really Cleaner Than Humans’?


There is an age old adage that states “a cat’s mouth is cleaner than a human’s mouth.” This claim that felines have the cleanest mouths has been stated for years, though the science and research behind it has been dubious. With new studies evaluating oral bacteria and dental health of pets, we now have the ability to truly assess this common claim about cats having the cleanest mouths.

The question around whether cats truly do have the cleanest mouths compared to other animals has created debate between pet owners, veterinarians and scientists. Proponents of the claim argue that cats spend much of their day grooming and licking their fur, mouths and paws through a self-cleaning process. Critics argue that cats harbor just as much bacteria in their mouths as other animals. This article will dive into the evidence and research around bacteria, dental health and oral physiology to determine if science supports the notion that cats have the cleanest mouths.

Anatomy of the Feline Mouth

Cats have a unique mouth structure adapted for hunting, eating, and grooming. Their mouths contain 30 adult teeth including incisors, canines, premolars, and molars (FirstVet). The incisors and canines are sharp, pointed teeth designed for efficiently grabbing, killing, and tearing meat. The premolars and molars have more complex surfaces for shearing and grinding food. Cats also have a rough tongue that can scrape meat off bones and remove fur during grooming.

Cats have extra long upper canine teeth that interlock with the lower canines. Their jaw structure allows the upper canines to pass by the lower ones for maximum biting efficiency. Cats also have more teeth behind their canines compared to other carnivores like dogs. These rear teeth help cats crush bones and hold struggling prey (PetPlace). Overall, the feline mouth anatomy supports their role as an obligate carnivore.

Saliva Composition

Feline saliva is made up of water, enzymes, electrolytes, antibodies and antimicrobial compounds. Some key components include:

  • Fel d 1 – a glycoprotein and the primary cat allergen. It is found in higher concentrations in male cats. (
  • Lysozyme – an enzyme that damages bacterial cell walls.
  • Lactoferrin – a protein that deprives bacteria of iron.
  • Immunoglobulins – antibodies that identify and neutralize foreign objects like bacteria and viruses.

While human saliva also contains enzymes, electrolytes, and antibodies, there are some notable differences:

  • Human saliva does not contain the Fel d 1 allergen found in cats.
  • Feline saliva has a higher concentration of lysozyme and lactoferrin, giving it greater antibacterial properties.
  • Cats produce fewer carbohydrate-digesting enzymes like amylase in their saliva compared to humans.

Overall, the unique components of cat saliva, like Fel d 1 and high levels of lysozyme, make their saliva composition distinct from human saliva.

Grooming Habits

Cats are fastidious groomers and spend much of their awake time cleaning themselves. Their grooming regimen consists of licking their fur to remove dirt and distribute skin oils. Cats’ tongues have rear-facing barbs or hooks called filiform papillae that act like a comb or brush to smooth fur and remove knots and tangles [1].

This frequent self-grooming affects the bacterial populations in a cat’s mouth. As cats lick their fur, they transfer bacteria from their mouths across their bodies. One study found that the composition of oral and skin microbiota in cats is very similar, suggesting self-grooming disperses oral bacteria over the skin [1]. Interestingly, the grooming habits of cats likely help maintain healthier microbial populations. The mechanical action of the tongue removes dead skin cells and debris, and the saliva deposits antimicrobial substances.


A carnivorous diet that consists primarily of meat affects the oral microbiome differently than an omnivorous diet. Research shows that oral bacteria differs between vegans and meat-eaters ( Meat contains higher levels of fat and protein which can alter the pH in an animal’s mouth, selecting for bacteria that thrive in that environment. Cats, as obligate carnivores, have a GI tract adapted to processing animal flesh and absorb nutrients efficiently from meat. Their oral microbiome reflects this specialized diet.

In contrast, omnivorous human diets are more varied, consisting of meat, plants, grains etc. This variability allows for a more diverse oral microbiome equipped to process different macronutrients. However, the standard Western diet, high in refined carbs and saturated fats, can negatively impact oral bacteria. A healthy, balanced omnivorous diet supports a robust and diverse oral microbiome in humans (

Tooth Decay

Cats, like humans, are susceptible to periodontal disease and tooth decay (1). However, some veterinary studies suggest cats have a lower rate of oral health issues compared to humans. According to the NIH, over 90% of adult humans aged 20-64 have cavities in their permanent teeth (1). In contrast, one estimate puts the incidence of tooth decay in cats at only around 5% (2).

There are several factors that contribute to cats having healthier teeth and gums than humans on average. Cats are obligate carnivores and their natural diet consists of raw meat, bones, and other whole prey items. This diet helps clean cats’ teeth. Cats also groom themselves frequently, helping remove plaque and debris. Additionally, the composition of cats’ saliva may make their mouths less hospitable environments for bacteria that cause decay (1).

While cats do get periodontal disease and cavities at a lower rate than humans, oral health issues can still develop. Signs of dental problems in cats include bad breath, loose or infected teeth, reduced appetite, and excess drooling or pawing at the mouth. Catching dental disease early and providing at-home care, like tooth brushing, can help minimize problems (2).



Bacteria Types

Cats tend to harbor different bacteria in their mouths compared to humans. Some of the most common bacteria found in cat mouths include Fretibacterium, Peptostreptococcus, Pasteurella, and Capnocytophaga. Humans, on the other hand, commonly have Streptococcus, Actinomyces, and Staphylococcus bacteria in their mouths.

One study characterized the oral microbiota of cats and found Fretibacterium and Peptostreptococcus were the most predominant bacteria. These bacteria are not typically found in human mouths. Conversely, Streptococcus and Staphylococcus bacteria dominate the human oral microbiome but are less common in cats.

The bacterium Capnocytophaga can be found in both cat and human mouths. However, the strains tend to differ between the two species. Cats may harbor C. canimorsus, whereas humans are more likely to have C. ochracea or C. gingivalis strains.

While Pasteurella is common in cats, it is rarely found in healthy human mouths. However, Pasteurella infections can be transmitted from cats to humans through bites or scratches. This highlights an important difference between the bacterial flora of feline versus human mouths.

Bite Strength

Cats have extremely strong jaws and bite forces for their size. The average house cat has a bite force of around 200 pounds per square inch (psi) according to this source. Larger wild cats like jaguars can have a bite force over 1500 psi, which makes them the cat with the strongest bite pound for pound.

This powerful bite strength allows cats to quickly and effectively capture prey and defend themselves. However, it also means their bites can easily puncture skin and transmit bacteria into wounds. Cat bites have the potential to cause deeper tissue infections than other types of animal bites due to the shape of their sharp teeth and the force exerted.

So while their mouths are well-adapted for hunting and survival, this also makes cat bites more prone to infection than the bites of many other domestic animals. Proper treatment and cleaning of cat bites to the skin is essential to avoid complications from the transfer of oral bacteria.

Assessing the Claim

There is evidence on both sides of the argument about whether cats have cleaner mouths than humans. On one hand, some research shows that cats’ mouths contain fewer cavity-causing bacteria like Streptococcus mutans than human mouths do ( Their saliva also contains antibacterial enzymes that inhibit bacterial growth. Additionally, cats are fastidious groomers that frequently lick and clean their fur and mouths.

However, other evidence suggests cats’ mouths may not always be cleaner. Their sharp teeth can accumulate tartar and plaque over time if not brushed regularly. Bacteria like Pasteurella multocida and Capnocytophaga canimorsus found in cats’ mouths can cause illness in humans. And while cats groom frequently, they often use the same saliva to clean their bodies as they use in the litter box. Overall the evidence is mixed.

In conclusion, while cats may have some oral health advantages compared to humans due to their natural saliva composition and grooming habits, their mouths cannot be definitively classified as “cleaner.” Proper dental care and hygiene is important for cats as well as humans to maintain mouth health. More research would need to be conducted comparing bacterial loads in cat vs. human mouths while controlling for dental hygiene practices in order to objectively assess this claim.


In summary, there are several key points that determine whether cats truly have the cleanest mouths.

On one hand, cats spend much of their awake time grooming and cleaning themselves. Their rough tongue removes debris and spreads antibacterial saliva across their coat. Cats also consume very little sugary food that promotes tooth decay.

However, cats have a mouth full of bacteria-laden teeth and gums just like any other mammal. Bacteria accumulates on their teeth and forms plaque, despite their dedicated grooming habits. Cats are susceptible to periodontal disease and other oral infections if dental care is neglected.

When the available scientific evidence is reviewed, the claim that “cats have the cleanest mouths” does not seem to hold true. While cat mouths may contain less overall bacteria than dogs due to diet and grooming behaviors, their mouths are not bacteria-free and still require dental care and cleaning to maintain oral health.

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