Cat Housesoiling

Veterinary Medicine, March 2009, pp. 140-144
(Dr. Jacqueline C. Neilson, DVM, March 2009)

Housesoiling is the number one behavior problem for of cats. Frustration from inappropriate urination and defecation can lead to outdoor banishment, relinquishment, or euthanasia. In one study, greater than 23% of cats given up to shelters had a history of daily or weekly housesoiling incidents.

There are three main causes of inappropriate urination/defecation in cats:

  1. underlying medical problems such as a urinary tract infection or lower urinary tract disease
  2. urine marking
  3. issues to do with the litter box.

These problems may overlap as well, such as a cat with pain from a lower urinary tract infection may develop an aversion to a litter box or litter type.

Many litter box problems stem from preferences to type of litter, box location, or type of box preference but they may also stem from outside factors such as inter-cat aggression, a cat that is frightened for some reason, or loud noises around the litter box.

A study in the early 1990’s identified cats’ strong preference for finely granular sand-like material, widely knows as clumping or scoopable litter, compared to large-granule litter, such as litter made of recycled paper, crystal litters, and wheat/cedar litters.

The litter market today offers a wide variety of litter products. Each category of litter also has several brands that have different additives to their litter. For example, a basic component of clumping clay litter is sodium bentonite. Multiple ingredients may be added to the sodium bentonite base, including fragrances, fillers, bacterial growth inhibitors, and absorption additives, to create a unique litter product. The impact of fragrance added to litter is unclear. In one study, scented litter increased the risk of inappropriate urination, but in another it was not associated with elimination problems. Nevertheless, if a cat has a housesoiling problem and they are being offered a litter with fragrance, it is warranted to try one that is non-scented. Little data is published on sent preferences of cats, but a 2007 pilot study with seven cats showed a preference to cedar and fish odors and an avoidance of citrus and floral scents.

Odor control continues to be an important aspect of elimination problems. While daily scooping and discarding of solid waste are strongly advised, additional techniques to control urine and fecal odor are desirable. Activated carbon has been incorporated in some litters in an attempt to decrease odors. A study was done comparing cat’s preference to a litter with or without activated carbon. The results showed that cats preferentially used the litter with the activated carbon. A similarly designed study involved 32 cats compared Fresh Step Scoopable (The Clorox Co.) with activated carbon and Arm & Hammer Super Scoop (Church & Dwight) with sodium bicarbonate (another odor eliminator). These two litters not only had different odor controlling ingredients, but also contained different fragrances and fillers. There was a statistically significant difference in cats preferring the Fresh Step Scoopable litter (Neilson J, Portland, Or, Unpublished data, 2008).

Box size has long been explored as a cause of housesoiling. Some experts recommend that litter boxes be 1 ½ times the cat’s body length. No clinical studies have supported this recommendation. Dr. Neilson conducted a clinical study on 32 cats in a shelter giving them a small, medium, and large litter box. There did turn out to be a statistical preference to the large box, so offering as large of a box as possible may be helpful. Some people even purchase large plastic storage boxes to use as a litter box.

In summary, it appears that cats prefer clumping litters with activated carbon added for odor. If a fragranced litter is going to be used, data suggest a cedar preference or at least avoidance to a citrus scent. Finally, based on trends noticed in the box size study, purchasing a jumbo-sized litter box is advisable. It is possible to come across a cat with unique preferences as well. The best way to identify an individual cat’s set of preferences is to offer a variety of litter choices and box styles and keep the combination that the cat prefers. It is also wise to remember that no odor-controlling litter ingredients can substitute for daily litter box scooping and regular box washing.


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