Why does cat urine smell so bad and why is it so hard to get rid of?

While trying to get rid of cat pee smell I got to wondering why it smell so bad and why it had proved to be so difficult to remove. After much research I found that the answers are not straight forward at all. This page reports on what I found out so far.

Cat urine purpose

Urine is a liquid containing water and soluble waste products. It is filtered by the kidneys from the blood. From the kidneys the urine flows to the bladder where it is kept until the cat pees. When this happens the urine flows out through the urethra (and penis in males).

Another purpose of urine is as a way of carrying signal chemicals cats use to communicate with other cats. These pheromones and other chemicals are often very odorous.

All cats can squat and pee, that's the usual way for females and males to get rid of waste. Males can also mark. We have all seen male cats back up to a spot and wiggle their tail as they spray and mark their territory.

Although most urine products are filtered out from the blood some are actually made in the kidneys. This is particularly true of the pheromones.

Cat urine is concentrated

Because cats evolved from desert areas, they have a more concentrated urine. This is a method of saving water often used by desert animals.

This helps explain why cats are subject to urinary track blockages. The high concentration of salts in the urine means that they are more likely to crystallize and form blockages. This also explains why kidney stones are also not an uncommon occurence in cats.

The concentration of cat urine also depends on how much the cat drinks. Vets often urge cat owners, particularly if their cats have urinary track problems, to encourage their cats to drink more, and to feed wet food instead of dry to increase water intake.

The amount of water in cat urine can fluctuate a lot. If a cat does not drink much, is fed a dry diet, or is avoiding using the kitty litter because it's afraid, or the litter is dirty, or because the animal is sick, then the urine will be more concentrated.

What is cat urine made of?

Cat urine is not a fixed formula. It varies with the age, sex, whether the cat is neutered, its stress level, its diet and how much it drinks, and its health including any medication it is taking.

Cat urine has 2 specific functions. It is a mean of getting rid of soluble waste products, particularly the nitrogen waste products. This is consistant biological need, and all cats will have these waste products in their urine

Besides waste products urine also contains a large number of communication chemicals called pheromones.

Main waste products

Urea, 2% is by far the the main waste product in cat urine. A small amount of the more toxic Ammonia .05% and Uric Acid .003% is also produced.

Uric acid and Urea solubility in water is quite low and this makes it very difficult to clean up after the urine has dried. Even after careful washing much remains behind to be broken down by bacteria and produce smelly ammonia.

The breakdown of Nitrogen rich urea and uric acid, by bacterial action, into ammonia is the principal cause of smelly urine in cats.

Creatinine .1% is a waste by-product of normal muscle creatine phosphate breakdown. It's a fairly constant component of cat urine at about .1%.

Creatinine levels are commonly measured when you have bloodwork done on your cat. Increased creatinine levels are a good indicator of kidney disease and a good predictor of future life span.

There are various ions, the main ones are Sodium about .1% and Chloride about .6%

Phosphates .12% is excreted from extra phosphorus taken in the diet of the cat. Phosphorus is used to build and repair bones, the body also uses phosphorus in the nerves and muscles.

Sulphates .18% Sulphur is used in the body for several purposes. It is part of molecules that help cell grow and stick together, blood vessel synthesis, wound repair, hydration of tissues including eyes and mucus membranes and many other processes. Sulfur is also an ingredient of many smelly chemicals.

Of particular interest is the many organosulfur compounds that are used in feline pheromone communications.

If you are interested here is a link to Wikipedia article on Glycosaminoglycan which is a sulphur containing class of chemical that regulates and aids cell growth and various other processes.

Urobilin is the chemical that colour the urine and feces, and can stain fabrics.

There are also various electrolytes and of course pheromones. Although urine is often thought of as sterile, bacteria has been found in healthy cat urine.

This is not all that is found in cat urine, only the main ones. These are products of regular metabolic functions and will be found in males and females, neutered and intact. Pheromones however is another story.

Communication chemicals in cat urine

Cats are experts in communicating using Pheromones, (communication chemicals).

These chemicals are complex and numerous (they can total over a hundred) to accommodate the various messages to be delivered.

What chemicals are found depends on many factors. Sex and whether the cat has been neutered has a great deal of importance. Age and health, and state of mind such as fear also play a role.

A cat might be marking territory, looking for a mate, challenging a rival, indicating they are young and should not be harmed, showing clan belonging or greetings, or might be emitting fear pheromones. Some pheromones are produced by mother cats to make their kittens feel safe and happy.

There are many greeting pheromones notably the ones cats rub with their face glands. A synthetic friendly greeting pheromone called Confort zone Feliway has been developed and helps calm cats and makes it easier for cats to get along, reducing spraying and aggression

Cats not only produce pheromones in the urine, but also in glands located in various spots of the body. There are anal glands that scent the feces, cheak and head glands, and also glands on their paws.

Studying cat pheromones is tricky because the quantities of the marking chemicals are often quite small it's easy to contaminate a sample, this is a great difficulty for scientists collecting samples. Even if the sample is collected uncontaminated, the chemicals often degrade quickly making them more difficult to find and study.

Most of the cat pheromones cannot be smelled by humans and are not very important except to cats. A few, however are very smelly. These often contain sulfur molecules.

Of note is Felinine. It is an organosulfur compound found in cat urine, which is often associated with foul odours.

Many of the skunk spray compounds are organosulfur compounds.

Pheromones are often fatty acids that are not readily dissolved by water. This makes the mark sticky and more persistant. This is useful to a cat marking his turf but annoying to someone trying to clean if off.

While I was researching this page I ran across a note that Lion Urine was used to keep dogs away from gardens. I'm sure it would work but I can't imagine trying to collect lion urine.

Cat pheromones have been developed by cats to communicate with other cats but prey animals such as rats and mice have also learned to recognize cat smells and to avoid them.

At least one parasite, Toxoplasma Gondii, has learned to modify the natural avoidance of cat urine by manipulating the rodent brain. Since they no longer avoid areas marked by cats, they are more likely to get eaten, and infect the cat. This lack of avoidance of cat urine has also been identified in humans infected with the parasite. (it is quite common and usually asymptomatic except in pregnant woman where it can do a great deal of damage to a developing fetal nervous system.)

More info on Toxoplasma Gondii if you are interested. Here is a transcript of an interviw by Dr.Robert Sapolsky whose lab has studied this phenomenom.

Conclusion, why does Cat Urine Smell bad.

Cat pee smells bad because it contains Urea and other nitrogen compounds that are decomposed by bacteria to Ammonia which have a strong smell. A second source of bad smells is from the cat pheromones used to mark territory and transmit other information to neighbourhood cats.

In order to get rid of cat smells, both sources have to be fixed. Here is a link to my article Getting Rid of Cat Urine Smell.

emails: Christine

This article is provided for information and entertainment only. Test any cleaning product before using. Most products used to get rid of urine smell contain enzymes that are quite safe, however some of the cleaning products that may be included could be more toxic. Read the label.