How to find pet urine stains with a black light

How can you find where your pet urinated in your home? Yes, you can smell it. But where is it? One important part of solving your cat’s litter box problems or your doing peeing inside is to clean all the locations where they peed.  This is because your pet can smell it and knows that’s where they’ve urinated before, so they are likely to do it again.

But how do you know where your pet peed in the past when it’s dried?

In this article, we are going to teach you how to find pet urine stains using a black light.

What is a black light, and how can it find pet urine?

Black light is also known as ultraviolet, or UV, light. UV light, simply, is light with a frequency higher than visible light. However, it’s not necessary to learn physics right now. Just think of a rainbow.

Water crystals break visible light into a spectrum where red has a lower visible frequency and violet has a more highly visible one. Anything lower than red is called infrared (which can be sensed as heat but you can’t see it), and anything higher than violet is ultraviolet.  This is why it’s known as black light, because it’s not visible.

Black light has many applications. For example, most paper money and some documents have markings that are visible under black light to prevent counterfeiting. UV light is used in the medical field for sterilization and disinfection purposes. Even swimming pools and drinking water ican be disinfected using UV lighting. Tanning beds use black light to stimulate additional Vitamin D production in your skin, eventually creating that supposedly healthy glow. Or was that just back in the 70’s?

UV light is also used in art to create drawings visible only under UV lighting. Body fluids, such as blood, urine, and semen, are easier to detect under UV light. For this reason, UV lights are used in crime scene investigations. Have you ever seen a purple toilet? It’s so the staff can see where one has urinated over the edge.

See where this is going? Pet urine literally glows when exposed to the black light. Even long after urine has dried, its scent-creating chemicals will still be visible, thereby making pet urine stains (including older ones) easy to find.

What type of black light devices should you use to find pet urine?

Many types of black light devices are available on the market, with varying prices and sizes. The most popular are bar-type lamps, which use fluorescent UV bulbs, and small LED flashlights.

Although light strength can vary from maker to maker, LED lamps are generally stronger. They are considerably stronger if you need to find cat urine. By stronger, we don’t mean the actual visible light, which does not make cat urine glow, but rather the amount of UV light it emits.

The most important feature to look for is wavelength.  UV light wavelengths may vary from 10 to 400 nm (nanometers, or billionths of a meter). Most blacklight flashlights are marked to indicate what wavelength they emit. You’ll most likely see LED lamps with 400 nm, 385 nm, or 365 nm in general stores. Try to avoid lamps with a wavelength of 395 or 400 nm. They are less useful in finding pet urine because they are very close to being visible light. For best results, we recommend going with 365 to 385 nm UV lights.

The number of LED bulbs also makes a difference in how easy it is to find pet urine. For household use, you can easily go with 9 or 12 LED bulbs in a blacklight flashlight. As you can imagine, the more UV LED bulbs a flashlight has will increase the price.

You can find blacklight lamps online. Click here to check out the UV flashlight we have, from Amazon.

A good UV LED flashlight should cost no more than $20 to $30, which means that the technology is affordable as a household item.  It’s not high-end technology that is only available to scientists. You can find cheaper ones, too, but most of them perform poorly because the UV light they emit is not optimal for finding pet urine.

How do you find pet urine using a black light?

You now have the equipment, you are ready to find the “evidence” that is left on your floor, carpet, and furniture. It’s as simple as point and look, but following are a few tips to improve your search.

It will be easier to find pet urine if you darken the room. Search in the evening, or with the blinds closed and lights out. Pet urine will still glow under UV in broad daylight. It’s just a little harder to find as you’ll have to point the light right down onto the surface to notice it.

Turn the black light on and shine it on different surfaces. In general, if you are looking for house-soiling locations, you must look on all the horizontal surfaces, including bed sheets, furniture tops, bookshelves, your clothes, and even in sinks and bathtubs. If your cat is spraying urine, look on vertical surfaces as well, especially near doorways, passages, and corners. Find more about urine spraying here.

Turning on the black light the first time might be scary because everything may be glowing. Actually, there are several substances that glow in black light conditions, including some types of wallpaper glue.

All you have to do is determine whether what you are seeing looks like something else. Generally, you are looking for yellow splatter or individual spots. On vertical surfaces, you are likely to observe a single drop that has run down the wall before drying out. This video shows what urine looks like when viewed under a blacklight:

If your dog has been urinating in the house or your cat outside of the litter box for a while, you will see bright spots and weaker spots. The weaker spots are older and contain less of a concentration of chemicals that glow. Bad news for us, because your pet is still able to sense where they peed or dribbled.

Mark the locations where you find spots, as you won’t be able to see them when you turn the black light off. Anything will do, but we’ve found some Legos, or other small objects work well to outlight the area or mark the exact little spot.

Next, treat all the discovered locations with a cleaner intended for pet urine removal. We found Nature’s Miracle in the red bottle works wonders. It has enzymes to remove the proteins in the stains.  It also helps remove the scent so your pet is less likely to “revisit” the same spot. Make sure to clean an area a little larger than the area you found with the blacklight flashlight. Find out how to clean pet urine here. First, doing so leaves no room for error. Second, pet urine tends to soak into surfaces (especially carpets), and what you see under a blacklight may just be the tip of the iceberg.  If it’s on carpet, you may find that the padding underneath has also soaked up the urine.

Remember that knowing how to find pet urine is not the hardest part. Finding the urine is just a single step in a path to making your house free of pet problems. For dogs, teaching them through positive reinforcement to urinate (and poop) where you want is the best course of action. You know known when they usually have to go, like right after they wake up or eat. Take them outside or where you want them to go. Teach them by giving them a command (we used “Get Busy” with ours). When they pee or poo, give them a treat and praise them.  They’ll figure it out very quickly. additional help with a cat urine problem, please check out our article series about cat litter, litter boxes, and cat house-soiling problems here.