Pet & Animal: How to Find Cat Urine With a UV Light

The smell of cat urine is strong and unpleasant, but the stains can sometimes be hard to find! Luckily, you don’t have to rely on your nose alone to help you find the source of the odor. Instead, try using a UV light, also known as a black light. If you shine the light in a dark room, cat urine will glow yellow or green, making it easy to see exactly where you need to clean. Once you find the spot, neutralize the urine with an enzyme cleaner!

EditSteps

EditLocating the Urine

Purchase or borrow a UV light between 365-385 nm. For the best results, look for a handheld LED light with 9-12 bulbs. It should be rated between 365-385 nm, which stands for nanometers. A lower rating won’t be strong enough to light up the cat urine, and a higher rating is too similar to natural light to have an effect.^[1]
- You can find these lights online or at a local home improvement store.
- You can also find UV lights with fluorescent bulbs. As long as it’s rated between 365-385 nm, this will work as well, although the LED lights tend to be stronger.
Wait until evening and get the room as dark as possible. While you could try to draw all the curtains in the room as tightly as possible, it will be easier to wait until it gets dark outside before you try to use the UV light. When you’re ready to start looking, turn off the lights in the room, as well as the lights in any adjacent rooms or hallways.^[2]
- If the room isn’t dark enough, your eyes won’t be able to detect the glowing urine.
Go to the area where you suspect the urine is located and turn on the UV light. Typically, the urine spot will be somewhere in the area where you can smell it, although sometimes you’ll have to look around a little before you find it. To make the search more efficient, start searching near where you think the cat may have urinated, then work outward.^[3]
Look for a glowing yellow or neon green spot. When the UV light comes into contact with the urine, it should start to glow. Depending on how much urine there was, and where it is located, the stain may look like a spot, puddle, splatter, or drips.^[4]
- For example, if your male cat sprayed to mark his territory on the wall, it may look like a splatter, with a few drips running down the wall. If the cat peed on the floor, you might just see a large round-ish spot.
- Some cleaning products and other household materials, including wallpaper glue, may glow under a blacklight, so don't panic if your whole room lights up when you turn on the UV light.
- Other substances, including some bodily fluids and tonic water, may also glow. Use the location, size, shape, and smell of the spots to determine if it's cat urine.^[5]
Sweep the light back and forth, checking various surfaces. Cats may sometimes urinate on a variety of different surfaces, so don’t just check the floor. Slowly move the light from side to side, checking along the walls and door frames, on top of and on the sides of furniture, and on any bedding in the area.^[6]
- If you don’t spot the stain right away, slowly move outward from the source of the odor.
Mark the edges of the stain so you’ll know where to find it. It can be hard to remember exactly the size and shape of the stain when the lights come back on. To ensure you know exactly where you’re supposed to clean, use something like tape or chalk to mark a perimeter around the stain.^[7]
- It’s a good idea to clean further outside of the stain than what you can actually see, in case the stain soaked in and spread out, so don’t worry about perfectly defining the edges. Just make a small mark at the top, bottom, and sides of the stain so you’ll remember where it was.

EditCleaning the Spot

Try to find and clean the stain as soon as you can. It's not always possible, but the sooner you can get the stain clean, the better your results will be. If you smell cat urine and you can’t find the stain during the daylight hours, try to use the UV light to locate the spot that same evening.^[8]
- Cat urine will smell stronger as it breaks down. It will also be harder to clean once it’s set in.
Saturate the stain with soapy water if it’s possible. If the stain is somewhere that’s safe to get wet, like your carpet, mix a few drops of dish soap into warm water, then blot the water over the entire stain. Leave it there for about an hour. This will help to loosen the crystals from the cat urine.^[9]
Blot away the stain with a damp cloth. Once the soapy water has had enough time to penetrate the stain, blot at the area with a damp, clean cloth. Work from the outside in to avoid spreading the cat urine out past its original spot.^[10]
- If you’re trying to clean something that can’t get wet, like leather or wood, skip soaking the area and just blot away as much of the stain as you can with the damp cloth. Let the area dry completely.
Spray the area with an enzyme cleaner and let it sit for 20 minutes. There are a number of different cleaning products available on the market for use around the home, but to completely neutralize the urine, you’ll need an enzyme cleaner. Saturate the area completely, remembering to apply the cleaner beyond the edges of the stain in case it spread as it soaked in. Directions may vary, but typically these sprays don’t need to be wiped away.^[11]
- You can find enzymatic cleaners at pet supply or home improvement stores, or you can even make your own if you want to.
- Be sure to read the directions on the product you’re using to make sure it's safe for the surface you need to clean. You may also want to spray a little of the cleaner on an inconspicuous area to make sure it won’t damage the finish of whatever you’re cleaning. Enzyme cleaners are typically gentle compared to other cleaning products.
- You can find powdered enzyme cleaners if the item you're cleaning can't get wet.