The Stinky Truth About Cat Spray. Why It Smells So Bad


The strong, pungent odor of cat urine is a common complaint among cat owners. While cats are known for their cleanliness and self-grooming habits, their urine can produce powerful odors that many find unpleasant or overpowering. Understanding what makes cat urine smell so potently can help cat owners manage litter boxes and clean up accidents more effectively.

A cat’s sense of smell is 14 times stronger than humans, so what may smell potently to us is normal to cats. The unique makeup of a cat’s urine contributes to its strong odor, especially as the urine breaks down. By looking at the chemical composition and how it compares to other animals’ urine, we can better understand the science behind that distinctive cat pee stench.

Chemical Composition

Cat urine contains a complex mixture of chemicals that give it its characteristic pungent smell. Some of the key components include:

Pheromones: Cats produce pheromones like felinine and 3-mercapto-3-methylbutan-1-ol that transmit territorial signals and attract potential mates. Pheromones are volatile and release smells as they degrade (

Proteins: Cat urine contains proteins that break down into foul-smelling amino acids like cadaverine and putrescine ( Bacteria further break down the proteins, intensifying the odor.

Fatty acids: Cats produce volatile fatty acids that have a rancid, cheese-like smell. These include isovaleric acid, isobutyric acid, and butyric acid (

In addition, the urine contains waste products like ammonia that add to the strong scent. The combination of all these chemicals makes cat spray a potent and unpleasant-smelling liquid.


Cat spray contains pheromones, which are chemical substances used in animal communication. Cats have pheromone-secreting glands on their cheeks, lips, chin, forehead, tails, and between their paw pads. When a cat rubs against people or objects, it deposits pheromones from these glands. This scent marking serves to claim territory, advertise sexual availability, and spread soothing messages.

There are two types of pheromones in cat spray:

Feline facial pheromone (FFP) – Conveys reassuring messages to cats and helps them feel calm and comfortable. Commercial pheromone products like Feliway contain synthetic versions of FFP.

Feline interdigital semiochemical (FIS) – Found between the toes and leaves scent messages for other cats. FIS pheromones mark territory and advertise mating readiness.

The powerful pheromones in cat spray are used for territorial marking and finding mates. When cats sense these pheromones, it triggers innate behaviors and responses.

Protein Breakdown

One of the primary reasons cat spray smells so terrible is because of protein breakdown. As proteins degrade, they break down into smelly volatile compounds like methanethiol, dimethyl trisulfide, and other sulfur-containing molecules (Higgins 2008). Cat urine contains large amounts of protein from waste products. When this urine is sprayed and allowed to sit, proteases like urease catalyze the breakdown of urea and proteins into smaller compounds.

The proteolytic degradation of proteins and amino acids by enzymes produces many malodorous volatile sulfur compounds that give cat spray its potent stench (Higgins 2008). Though other components like fatty acids and ammonia contribute, protein breakdown is the primary source of the unpleasant volatile compounds that make cat spray smell so terrible.

Fatty Acids

One of the main components of cat urine that contributes to its pungent smell is fatty acids. According to this source, the fatty acids in cat urine make it sticky enough to adhere to surfaces and emit odor for weeks. As the urine breaks down, these fatty acids vaporize into the air and produce a strong, unpleasant smell.

An article from Crookston Pet Clinic explains that detergents help remove urine odor by getting rid of the fatty acids. The fatty acids contain smelly volatile organic compounds that vaporize at room temperature. This vaporization process spreads the odor into the surrounding environment.

The chemical structure of the fatty acids allows them to linger and produce lingering odors. Removing cat urine smell requires directly addressing these fatty acids before they can vaporize.


Ammonia is one of the main culprits behind the pungent smell of cat urine. It is formed when bacteria in the urine break down urea, which contains nitrogen. According to Catster, the ammonia smell gets stronger as the urine ages because more bacterial decomposition occurs over time. The ammonia gas released is quite irritating to both humans and cats.

Some additional ammonia is also excreted in the urine directly. A higher concentration of ammonia can indicate more concentrated urine, which may be a sign of kidney disease, according to Armand Hammer. So a sudden increase in that strong ammonia odor in your cat’s urine is worth getting checked out.


As cat urine begins to break down, the urea in the urine is converted into ammonia by bacteria growth. This bacteria growth is what produces many of the odors associated with cat spray (McGill University, 2022). The bacteria feed on the proteins and fatty acids present in the cat urine, decomposing them and releasing foul odors in the process. One study found that compounds produced by bacteria growing in cat urine can even be detected by humans over long distances, triggering avoidance behaviors (Flegr, 2011). The bacterial metabolites that produce the strongest odors include ammonia, indoles, mercaptans, and fatty acids. These are all byproducts of the bacteria digesting and decomposing the organic compounds present in fresh cat urine.

Bacteria levels peak between 5-14 days after the initial cat spraying incident. During this time, the bacteria are rapidly feeding and reproducing, creating exceptionally strong odors. As the available “food” decreases over time and conditions become less favorable, the bacteria begin to die off and the odor dissipates. However, without proper cleaning, enough bacteria may remain in carpet or fabrics to return with a vengeance if they get wet again (McGill University, 2022).

Comparison to Other Animals

Cat urine has a uniquely strong and unpleasant odor compared to many other animals (source).This is primarily due to the high concentration of ammonia typically found in feline urine. Cats’ bodies are highly efficient at extracting nutrients from food, meaning their urine contains more concentrated waste products (source). The average cat’s urine has an ammonia concentration of 2-3 times that found in dog urine. When cleaning messes, the ammonia odor from cat urine is often still detectable even after the stain has been removed. The high ammonia content causes cat urine to have a sharper, more pungent smell compared to many other pets.

Removing the Odor

The strong scent of cat spray can linger, but there are several effective cleaning products and methods to remove the odor.

Using an enzyme cleaner specifically formulated to eliminate pet odors is highly recommended. Enzyme cleaners work to break down the proteins and acids in cat urine that cause lingering smells. Popular brands like Nature’s Miracle contain active enzymes and bacteria that target urine and fecal odors and work to fully eliminate the smell. Be sure to thoroughly soak the soiled area and allow it to dry completely.

Another effective cleaning solution is white vinegar diluted with water in a 1:1 ratio. Vinegar is acidic which helps neutralize alkaline compounds in cat urine responsible for the odor. Wipe the area down with the vinegar solution and let air dry. The vinegar smell will fade as it dries. This can be used on surfaces like floors, walls, and furniture.

Baking soda is another natural odor neutralizer. Allow the baking soda to sit on the sprayed area for several hours to fully absorb the smell before vacuuming up. Sprinkling additional baking soda before vacuuming can help remove any lingering odors from carpet fibers or upholstery. The key is being patient and allowing the baking soda time to work.

For severe cases, deep cleaning with an extraction machine may be necessary. Carpet shampoos and wet vacuums can penetrate below the carpet surface to remove urine that has soaked into the padding. This is the most thorough way to eliminate cat spray odors from carpeting.


To recap, the strong and strange odor of cat spray is the result of a complex combination of chemicals. The spray contains pheromones that send social signals to other cats, as well as protein breakdowns, fatty acids, and ammonia from urine breakdown. Certain bacteria can further enhance the smell. While humans find the odor quite unpleasant, for cats it provides an important means of communication and territory marking.

Understanding why cat spray smells the way it does enables cat owners to approach it with more empathy, and to take steps to reduce or remove the odor more effectively. Overall, the science behind cat spray’s notoriously bad smell highlights both the differences and similarities between cats and their human companions.

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