Dear Christopher Cat: I smell cat urine in my house, but I don’t know where it is. How can I find it, and what should I do about my cat, Whiskers?

Christopher Responds: Urine gives off a fluorescent yellow-green glow when you illuminate it with ultraviolet light, also called black light.

You can buy an inexpensive black light from a store that sells posters to teens. When it’s fairly dark, walk around your home and shine your black light on the floors and upholstery.

You’ll probably be surprised at what you find. Be forewarned, though, that some dust speckles fluoresce, too.

When you find a yellow-green glow, dowse it with copious quantities of an enzymatic cleaner, such as Nature’s Miracle or Simple Solution. Follow the directions on the label, and you’ll be delighted to walk into your home and smell freshness – without a trace of cat urine in the air.

Take Whiskers to the veterinarian, explain where you found the urine stains, and ask the vet to run a urinalysis. Based on the information you give, the physical exam, the urine test results, and possibly blood work or bladder x-rays, your vet will be able to formulate an effective treatment plan so this problem doesn’t recur.