Pet Urine Smell Came Back After Cleaning: Why and What to Do

This guide covers why a pet urine smell can return after you clean, especially after shampooing the carpet or on humid days: urine below the surface, heat and steam, leftover cleaners, repeat treatments, padding, and when to call a professional. It uses what the Carpet and Rug Institute (CRI), the IICRC, the AKC, Humane World for Animals, Ohio State University and the City of Long Beach say.

Urine that soaked below the surface

The AKC's answer to "Why does my house still smell after cleaning dog urine?" is:

"Urine may have soaked into padding, upholstery, or wood. Repeated treatments or professional cleaning may be necessary."

Humane World for Animals says: "Your job will be more difficult if urine has soaked down into the padding underneath your carpet. In some cases, you may need to replace portions of carpet and padding." The CRI's technical bulletin on pet urine says, about cats: "Unless the cat urine can be completely removed, complete odor removal is unlikely."

Not sure where the smell is coming from? See Why Does My House Smell Like Dog Pee? Finding the Source.

Sources: AKC, How to Get Rid of Dog Pee Stains and Smells; Humane World for Animals, How to Remove Pet Stains and Odors; CRI, Technical Bulletin: Pet Urine and Carpet.

Why it comes back after shampooing or on humid days

The IICRC tip sheet quotes its S100 carpet cleaning standard:

"Elevated heat and humidity created from the cleaning process can amplify odors, so they are more evident during and after cleaning and during warm, humid conditions."

The CRI technical bulletin says: "A number of products are available to combat odor, but some may simply mask the odor, and, in times of high humidity, the odor may reappear."

Sources: IICRC Consumer Floor and Furnishings Care Information (PDF); CRI technical bulletin.

Spots that reappear as the carpet dries

The IICRC calls reappearing spots after cleaning "wicking". Its tip sheet says:

"Regardless of the method used, carpet cleaning cannot always remove 100% of the soil deeply embedded in the carpet fibers."

"This soil can move from the base of yarns and backing materials to the yarn tips, where it becomes a visible stain again after the carpet dries."

That section is about soil in general. On spills, the same tip sheet says: "If the liquid penetrates through to the backing or padding, the dye stain may return after the carpet dries." For marks left on light carpet, see yellow pet urine stains on light carpet.

Source: IICRC tip sheet.

Heat and steam can set the smell

The CRI says: "Don't use a steam cleaner when dealing with urine spots because the heat will set the stain and the smell." Humane World for Animals says: "Avoid using steam cleaners to clean urine odors from carpet or upholstery. The heat will permanently set the stain and the odor by bonding the protein into any man-made fibers." The AKC agrees: "Avoid heat or steam, which can lock in urine odors".

The CRI's alternative: "Instead, extract the spill with a wet vacuum and rinse with cool water to reduce the odor."

Sources: CRI, Cleaning and Maintenance; Humane World for Animals; AKC.

Leftover cleaner from earlier attempts

A pet odor handout on the City of Long Beach website says:

"If you've previously used cleaners or chemicals of any kind on the area, then neutralizing cleaners won't be effective until you've rinsed every trace of the old cleaner from the carpet."

"To remove all traces of old chemicals and clean old or heavy stains in carpeting, consider renting an extractor or wet-vac from a local hardware store."

The IICRC adds that "It is often impossible to completely restore the original appearance of a textile furnishing that has been damaged with aged pet urine, especially if homeowners attempt to remove the urine using the wrong products or methods."

Sources: City of Long Beach, Successful Cleaning to Remove Pet Odors and Stains (PDF); IICRC tip sheet.

Enough product, enough time, and repeat treatments

For cat urine on carpet, Ohio State University's Indoor Pet Initiative says to blot first, then apply carpet cleaner or a dish detergent mix: "Saturate the area with this, and just let it sit on the area for an hour or two."

On repeating, the CRI Spot Solver page for dry urine says: "Complete removal may require repeating the same step several times." The IICRC says: "The size and penetration of the spill will also influence the amount of effort and number of attempts needed for complete removal."

For step-by-step cleaning, see How to Get Old, Dried Pet Urine Stains Out, How to Get Dog Pee Out of an Area Rug, How to Clean Pet Urine From Laminate and Vinyl Plank Floors, and how to get pet urine smell out of carpet on petcleanupkit.com. Whatever you use, the CRI says "you should still pretest any cleaner on a scrap of carpet or in an out-of-the-way area of your carpet."

Sources: Ohio State University Indoor Pet Initiative, How to Clean-Up Cat Urine; CRI Spot Solver, Urine, Dry; IICRC tip sheet; AKC; CRI, Cleaning and Maintenance.

When the padding or what is under it has to go

Ohio State's Indoor Pet Initiative says: "If the smell is bad and the cat continues to use this area despite all the cleaning, replace the padding underneath and clean the area under the carpet." The Long Beach handout says: "You may need to remove and replace that portion of the carpet and padding."

The CRI technical bulletin notes that spills can reach the cushion and the subfloor: "Some carpet manufacturers have developed backings that resist spills and even prevent the spillage from penetrating the carpet into the carpet cushion and, perhaps, the subfloor." The sources quoted here do not give steps for sealing a subfloor, so ask a flooring or restoration professional about that.

See our guide to pet urine in carpet padding.

Sources: Ohio State University Indoor Pet Initiative; City of Long Beach (PDF); CRI technical bulletin.

When to call a professional

The AKC says:

"If odors linger despite repeated cleaning, or if there are multiple or deep stains, professional cleaning may be the best option. This is especially useful for carpets, upholstery, and car interiors."

The CRI says: "If necessary, call in a certified carpet cleaning firm that knows how to remove pet stains and odors permanently."

Sources: AKC; CRI, Cleaning and Maintenance.

Why it matters for your pet

Humane World for Animals says: "As long as your pet can smell their personal scent, they may continue to return to the "accident zone."" See Why Do Dogs and Cats Keep Peeing in the Same Spot? On repeat accidents, it says: "If your pet is having regular accidents, have them checked by a veterinarian to rule out medical causes."

Source: Humane World for Animals.

Using P-Cleaner

P-Cleaner is the Pet Stain & Odor Eliminator Foaming Liquid from Pet Cleanup Kit. The product listing says: "Our rinse-free, water-based formula tackles the toughest stains and odors from urine, feces, vomit, and other organic messes on carpets, rugs, upholstery, and hard surfaces." It also says: "Works on carpets, upholstery, tile, and more.", "No scrubbing necessary" and "Odor-Free & Residue-Free". Test it on a hidden spot first, as the CRI advises above. Follow the directions on the product label.

Still hunting for spots? The full kit includes a black light.

Buy P-Cleaner on petcleanupkit.com

Quoted from the petcleanupkit.com product listing.