Why Do Shoes and Boots Smell Like Cat Pee?

In short: The “cat pee” smell is due to the release of ammonia. It’s a known problem with a polyurethane component in the sole breaking down and/or rotting due to exposure to water.

Some shoes and boots have a dark side: a powerful, repugnant smell that seems guaranteed to emerge after the shoe gets wet. The foul odor resembles cat urine. Here’s why.

Why do shoes and boots smell like “cat pee”

Assuming you do not suffer from foot odor, there are two possible reasons. Either a cat actually peed inside your shoes or boots, or a natural breakdown of materials has happened.

While the breakdown of materials can happen to any shoe, New Balance shoes, particularly the 990 and 993, have been known to produce this “cat pee” odor after a few months of wear.

Several people have also complained that their work boots have started to smell like cat pee. Indeed, the natural breakdown of materials can happen to both sneakers and work boots.

1. Make sure there isn’t actual cat urine

If your footwear smells like cat urine, you need to make sure that there isn’t actual cat urine. To do this, you will need a UV flashlight black light. A black-light is designed to detect body fluids.

Cat urine, in particular, glows very brightly under ultraviolet light. According to ThoughtCo., urine glows under a black light because it contains the element phosphorus. 

Urine also contains broken-down blood proteins that glow under a black light. If there is actual cat urine inside your shoes or boots, then you’ve figured out the culprit behind the nasty odor.

2. Natural breakdown of materials

If there is no actual cat urine in your shoes or boots, then it’s most likely due to the natural breakdown of materials, particularly the breakdown of a polyurethane component.

It has been a known problem with a polyurethane component breaking down and/or rotting due to exposure to water. The smell is due to the release of ammonia.

This natural breakdown of materials can happen to any shoe or boot, from any manufacturer. The key to preventing this issue is to make sure the footwear is completely dry if it ever gets wet.

For example, both my New Balance 990 and 993 would start to smell like cat pee after several months. No, I do not have a cat. The padding around the outside of the soles is porous.

Unfortunately, the material would hold moisture and provide a place for bacteria to grow. This, alongside the natural breakdown of polyurethane, would make my shoes smell like cat pee.

While it’s true that cat urine has a very strong odor, the ammonia odor we associate with the “cat pee smell” is actually the urea (waste products) in the urine breaking down in the litter box.

Urea is one of the waste products found in urine. It’s a byproduct of the breakdown of protein and can be broken down further into ammonia in certain situations.

As the polyurethane component of some shoes and boots break down and/or rots due to exposure to water, the release of ammonia produces an odor near-identical to cat urine.

How to get shoes and boots to stop smelling like “cat pee”

Now you know that the release of ammonia is the main culprit behind the cat pee smell produced by your shoes and boots. Luckily, there are several things you do to remove the “cat urine odor”.

1. Spray an enzymatic cleaner

If your footwear smells like cat pee, spray an enzymatic cleaner. It is formulated to help break down, neutralize, and remove extreme stains such as urine, feces or vomit.

An enzymatic cleaner is crafted to discourage repeat accidents. So, if your cat is the one to blame, you can prevent future urine disasters from happening again.

You can safely apply enzymatic cleaner directly to your shoes and boots. This particular product comes with a multifunctional three-in-one nozzle sprayer with foam, mist, and stream settings.

To use the enzymatic cleaner, spray the solution in and around your shoes or boots. Allow the enzymatic cleaner to work for 15 minutes, then blot up the stain with a clean cloth.

Then, allow your footwear to dry naturally for 24 to 48 hours.

2. Baking soda can help

Did you know that baking soda has the ability to neutralize the acid pH of many substances? Cat urine is slightly acidic in nature and baking soda works like a charm to fight the odor.

Additionally, dry baking soda powder can help absorb the humidity from your shoes and boots, which makes the conditions by which odor-producing bacteria thrive less desirable.

Sprinkle baking soda directly into your shoes. Shake the shoes around to distribute the powder. Let it sit for at least 24 hours to give the baking soda time to absorb the odor.

Before wearing the shoes or boots, shake out any excess powder. Your shoes and boots are now restored to freshness. Hopefully, the cat pee smell has disappeared.

3. Alternate your shoes and boots

To prevent bad odor from your shoes and boots, try to alternate them. Don’t wear the same shoes every day. If you wear the same pair every day, they don’t have time to dry.

Generally, it’s a good idea to alternate your shoes, especially if they are moist. Doing so helps to inhibit bacteria and fungus, both of which can contribute to the foul odor in your shoes.

Remember, our feet sweat throughout the day, and shoes soak it up. This means that your shoes and boots need time to completely dry before you wear them again.

Rotating your shoes can make them last longer, period.

Key takeaways

Now you know why boots and shoes smell like cat pee. The odor is most likely caused by the natural breakdown of materials, which releases ammonia. Or, a cat has peed in your shoes.