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Q: Why does my cat's litter box stink?

A: Poop can be removed with a scooper. So can a certain amount of urine, if you use litter that absorbs liquid and forms a clump. But the pungent reek of ammonia can still remain until the litter is changed or the entire box is cleaned.

No one likes the smell of ammonia, which has a characteristic odor best described as "decaying fish." As urine decomposes, ammonia is the primary compound released by odorant molecules. Urea, the primary component of urine, is odorless, but as it goes through bacterial decomposition, an enzyme called urease forms and converts urea into ammonia. Cat urine tends to contain a higher amount of urea than the urine of other animals, including dogs and humans.

Another chemical compound that contributes to the scent of cat urine is felinine, a urinary amino acid. Like urea, it has no odor until it starts to degrade. Then it releases sulfur compounds, known as thiols, that cause a sour odor.

Other factors include the cat's age and sex. Older cats typically have less efficient kidneys, and that can contribute to extra-stinky urine. Male cats also produce urine with an especially offensive odor, thanks to the presence of testosterone. They also have higher levels of felinine in their urine. To keep odor down, scoop every time you see that your cat has used the box. Dump old litter after two weeks and replace it with new and be sure to clean the box with warm water and a mild, unscented soap.

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