Why Does My Cats Litter Box Smell So Bad

Cat litter box odor is a very common problem for cat owners. According to a survey by Tuft + Paw, nearly half (44%) of cat owners report that their cat’s smelly litter box is their biggest hygiene concern in the home[1]. The odor can become overpowering and affect the quality of life for both cats and their owners.

There are many potential causes of litter box odor, ranging from diet to litter type to health issues. By understanding the various factors that contribute to smelly litter boxes, cat owners can take steps to reduce odor and keep their cat happy and healthy.


A cat’s diet can have a big impact on litter box odor. Certain foods are more likely to cause smelly poop and urine. This is because different ingredients can affect digestion and the smell of your cat’s waste.

High protein diets, especially those with lots of fish, tend to produce the smelliest litter boxes. Fish ingredients like salmon, tuna, and trout contain oils that cats struggle to digest fully. The undigested oils make their way into the cat’s feces and cause strong, fishy odors in the litter box. [1]

Other culprits are lower quality proteins and grains like corn, wheat, and soy. Your cat cannot properly digest these, so they ferment in the gut and create terrible smelling gas and feces. Choosing a high protein diet made with digestible ingredients like chicken, turkey, or lamb may help reduce litter box stench.

Litter Type

The type of litter you use can have a big impact on odor control. Here are some key factors to consider:

Clumping vs. Non-Clumping: Clumping litters are made of clay and bend together when wet, trapping moisture and odor inside the clumps. This makes it easier to scoop out urine clumps before smells spread. Non-clumping litters like crystals don’t clump as well. Clumping litters like Tidy Cats [1] are often better for odor control.

Scented vs. Unscented: Scented litters contain perfumes and fragrances to help mask odors. However, some cats dislike scented litter or are sensitive to the chemicals used. Unscented litters allow the cat’s own scent to remain. Natural litters like wheat or pine tend to be unscented.

Natural vs. Synthetic: Natural litters like wood, wheat, and corn tend to be more eco-friendly but don’t always clump as well. Synthetic litters like clay clump better to trap odors, but some cats don’t like the texture [2]. Finding the right balance for your cat is key.

Litter Box Location

The location of the litter box plays an important role in odor control. Poorly ventilated areas like basements or small closets can cause odors to linger. The smell gets trapped in a contained space without enough airflow to circulate the air. Placing the litter box in an area with good ventilation allows fresh air to enter and odors to escape.

Heat and humidity also exacerbate smells. The warmer and more humid the area, the more pungent odors become. Avoid placing the litter box in non-climate controlled spaces like garages or covered patios where heat and moisture can build up. The ideal location is a room with climate control, good airflow, and frequent human traffic to discourage the cat from spending long periods in the box.

Some good litter box location options are a main level bathroom or utility room with an exterior vent or window. Make sure the box is not crammed into a tiny space but has open areas around it for airflow. Also consider easy access for cleaning and a spot that has minimal fabric furnishings which can absorb smells over time.

Litter Box Size

One of the most common causes of a smelly litter box is having one that is too small for your cat. Just like humans, cats appreciate having enough space to move around and “do their business.” Boxes that are too small for your cat will get dirty rapidly as urine and feces collect with limited space for the cat to find clean spots. This leads to a buildup of odor.

The recommended minimum size for a litter box is 1.5 times the length of your cat. This provides enough room for them to turn around, dig, and cover their waste. You may need an even larger box if you have a large cat or multiple cats using the same box. Overcrowding is a key contributor to foul litter box odors.

With limited space, cats may end up soiling areas just outside the litter box since they don’t have enough room to get in the position they want. Some cats may refuse to use an undersized box at all. This leads to urine and feces on the floor around your home. Ensure your cat has a box large enough to accommodate their needs and prevent smells from spreading.

Cleaning Frequency

Frequent litter box cleaning is crucial for controlling odors. Feces and urine create ammonia gas as they break down, which produces a strong, unpleasant smell. The more waste that accumulates in the litter box, the more ammonia gas is produced and the worse the odor becomes.

Ideally, the litter box should be scooped at least once per day. Daily scooping removes feces and clumps before they get a chance to really break down and stink. This regular cleaning prevents ammonia and odors from building up over time. Some sources recommend scooping twice per day for households with multiple cats sharing a litter box.

While daily scooping is best, litter boxes should be cleaned at an absolute minimum of every 2-3 days. Allowing waste to sit for longer than this significantly increases odor issues. For people who work long hours or travel frequently, consider investing in a self-cleaning litter box to maintain regular cleaning.

Deep Cleaning

Deep cleaning the litter box periodically is crucial for controlling odors. According to veterinarians, you should do a full litter change at least every 2 weeks (Source 1). This involves dumping all of the litter, washing the litter box with soap and water, rinsing thoroughly, and adding fresh litter. The soap helps remove any residue or bacteria that can build up over time and contribute to smells.

Washing the litter box helps sanitize it and prevent odors from becoming ingrained in the plastic. Use a gentle soap and hot water, scrubbing all surfaces of the box. Avoid harsh chemicals or bleach that could leave behind fumes. Rinse several times until the soap residue is completely gone. Allow the box to air dry fully before refilling with litter.

Doing a full litter change more frequently, such as every week, can further help control smells. The litter gets saturated with urine over time, making odors worse. Scooping daily helps, but periodic deep cleans are still needed.

Health Issues

Certain health issues in cats can lead to foul-smelling urine and feces. One common cause is urinary tract infections (UTIs), which cause cats to urinate more frequently and in small amounts that do not properly get absorbed in the litter (Controlling Cat Litter Box Odor). The increased moisture allows more ammonia odor to be released from the urine. Anal gland issues can also contribute to foul litter box smells. The anal glands can become impacted or infected, leading the cat to express small amounts of foul-smelling liquid when defecating (What’s That Smell? Secrets Behind Litter Box Odor). Treating any underlying medical issues is important to resolving inappropriate litter box smells.

Preventative Measures

There are several preventative measures you can take to help control litter box odors before they start:

Use litter deodorizers and fragrances to help mask odors. Products like Arm & Hammer Clump & Seal have baking soda directly in the litter to help absorb odors.

Invest in air filters and purifiers designed to eliminate pet odors. Place them near the litter box area to help circulate cleaner air.

Litter box liners can help contain messes and smells. Look for thick, durable liners that won’t tear easily when removing clumps.

When to Seek Help

There are certain signs that indicate it’s time to take your cat to the vet for a checkup regarding litter box odor issues:

  • Sudden change in litter box habits, especially if your cat stops using the box altogether (https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/feline-behavior-problems-house-soiling)
  • Signs of pain or discomfort when eliminating, including vocalizations or frequent, prolonged trips to the litter box (https://www.aspca.org/pet-care/cat-care/common-cat-behavior-issues/litter-box-problems)
  • Blood or mucus in the urine or stool
  • Urinary blockage in male cats, which can become life-threatening quickly
  • Increased urgency or frequency of urination
  • Excessive licking of genital area
  • Urinating outside of the litter box

Behavioral issues may also need to be addressed, such as:

  • A dislike of the litter substrate or litter box location
  • Stress, anxiety, or marking territory
  • Underlying medical conditions causing pain or discomfort
  • Cognitive issues like dementia in elderly cats
  • Introduction of new pets, furniture, or household members

Consult with your veterinarian to identify the underlying cause and develop a treatment plan. Medical intervention, combined with behavior modification techniques, can help get your cat comfortably using the litter box again.

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