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Why Does Cat Urine Smell So Terrible?

catpee2Any cat owner can attest to the fact that cat urine is one of the strongest foul odors that exist in our reality. Feline urine has an undeniable pungency to it that seems relatively unmatched by other pets’ pee, and this is especially apparent when many different pets live in the same household. Being an owner of dogs and cats, it is very easy for me to differentiate between canine urine and feline urine (which comes in handy when trying to blame the source of an accident or mark). Out of the myriad of types of pets that I’ve had in my life, I can honestly say that my cats’ pee have been the worst. After reaching out to other cat owners (especially owners that have cats and dogs) and researching a bit online, I have concluded that this is a fact and here’s why:


Because they’re angry when they pee, which makes it smellier. Just kidding.

For starters, the reason why cat urine smells so strongly is because in general, it is much more concentrated than other creatures’ urine. It’s so concentrated because a cat’s lineage traces back to their desert dwelling days (why else do you think they instinctively go to the bathroom in a litter box of sand-like material?) and therefore their body systems are designed to use every last drop of water. This is a blessing of a survival technique, because it enables cats to stretch their body’s water supply for a long time! But it is also a curse (mostly for us), because when their kidneys squeeze out every last bit of moisture, not a lot of it remains when they actually urinate. So when they pee in their box, on the floor, on the bed, or in your backyard, they are releasing a high concentration of urea – which is the common compound found in all types of urine.


It’d be nice if they could just use a toilet…

Not only is their urine extremely concentrated with urea, but when the pee exits their body, it begins the degradation process. As the urine sits in a puddle or stain on the ground, microscopic bacteria are beginning to break it down – and the longer it sits, the smellier it will become! When the bacteria are basically consuming the urea (ew, gross), they are producing ammonia as a byproduct, which is adding an even worse tinge to the whole mess. The longer the urine spot goes unnoticed, the more ammonia is produced, and the worse it will smell, so that’s why it is particularly awful when a cat decides to “mark its territory” outside of the litter box. Due to their agile and curious nature, they are able to pee in places that are relatively hard to reach or see for us humans. Especially if it’s a random corner in a room that we never go into, or on top of a blanket set on a high wardrobe, we will smell the nauseating stench of a mysterious cat pee accident – but not know where it is. As the spot is further ignored, it quite literally rots as more bacteria grows on it and will release mercaptans (air particles found in skunk spray) becoming unbearable until it just becomes a permanent fixture in that room.


Oh…uhhhhh…..alrighty then…..

The only thing worse than this scenario (how could it get worse than decomposing pee?) is the fact that male cats (especially ones that aren’t neutered) have a lot more hormones and pheromones in their urine. This is nature’s handy dandy way of equipping males with the power to signal female felines nearby that there is a mate ready and available for action! He is also doing it to protect his “territory” from other males, so that he can save all of the females for himself (which is honestly very selfish and unnecessary). Usually if your male kitten is neutered before he hits kitty-puberty, he won’t “mark” or “spray” around your house, but it is still a possibility. Another terrible scenario is if your cat (male OR female) gets a urinary tract infection or kidney-related illness, because they will usually mark outside of their litter box to let you know they are sick. Not only are they peeing outside of the litter box, but it is also even STINKIER because of their affliction! I don’t really know if Mother Nature really thought through this urinary way of communicating…



Other situations that can cause an abnormally awful smelling urine, is if your cat is elderly, eating weird foods (particularly strong fish), or genetics. That’s right, your cat could just have the worst smelling pee ever for no reason at all except for genetics! However, if you do notice that your cat’s urine is much more pungent than it usually is, it could seriously signify a medical issue, so please check it out and make sure they are healthy. Read more about these illnesses here, and also how to get that horrid cat urine smell out of your stuff. Believe me, you’ll end up thanking me later!


Honestly, this couch should just be burned. It’s a lost cause.

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{ 7 comments… add one }
  • Ruth Pearl September 14, 2016, 5:01 am

    Enlightening and amusing… Thanks for the information. Too bad this knowledge doesn’t change the bottom line.

  • Ed Qualls September 14, 2016, 5:38 am

    The predominant chemical that distinguishes cat from dog urine is the degradation-product “3-mercapto-3-methylbutan-1-ol” (MMB), of the sulfur-containing amino acid “felinine,” produced specifically in feline urine.

    Both dog and cat markings contain urea, and dogs can and will also concentrate it for effect. While there are several, other compounds in dog urine that could be just as repulsive to humans, our noses appear to have been honed to identify chemicals unique to feline marking, in particular.

    One might hypothesize that sensitivity to this, and to other felid anal gland secretions, was a survival benefit, given that it’s one of the few ways our ancestors could have sensed that a feline predator was prowling the area— secreted behind a rock and ready to pounce—as opposed to the non-stalking canids, who typically use howling or yipping noises to establish their presence within a territory. (And our ears are well-attuned to those, too!)

    • VetDepot September 20, 2016, 10:35 am

      Wow, thank you so much for the information, Ed! 🙂 I may consult you in the future for further inquiries, you seem to be very knowledgeable!

  • Heather September 30, 2016, 9:06 pm

    Great info! My husband thinks I’m crazy when I say I can tell the difference between cat and dog pee!

    • VetDepot October 3, 2016, 2:53 pm

      Hahahaha! Yeah, non-animal-lovers don’t understand! 😛 A couple people told me, “Well all pee smells horrible,” and I was like…”Yes, but cat pee is especially AWFUL!!!” LOL

    • Brei March 30, 2018, 6:44 am

      My husband cannot smell anything due to having his nose broken and he thinks I’m crazy when I say I can tell the difference between cat and dog urin!!!! The dogs pee in the house and he will swear they didn’t??? NOW he says that the 3ft. diameter urine puddle in the kitchen this morning is the cats’ doing??? WTH!!! He says this because he blocked off the dog door to the kitchen last night Nooooooooo dear- she obviously urinated in the kitchen BEFORE you blocked off the gate I am losing my noodles

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