Scented Litter and Unscented Cat Litter - what's the difference?
Unscented cat litter is made without additional scent agents. Sometimes, unscented cat litter is called odorless litter; however, unscented cat litter will retain the smell of whatever it is made out of (clay, wood, corn, wheat, etc.). If you get an unscented cat litter with odor-absorbing additives like baking soda or carbon, it may smell like those things.
Scented cat litter contains additives that help cover or absorb those telltale litter box smells (ammonia, feces, mold). Odorants include fragrance, perfumes, deodorizers, or other natural or artificial scent agents. Sometimes an ingredient like carbon or baking soda is added in addition to the fragrance to help absorb litter box odors. Fragrances in scented litters are wide-ranging, from lavender, outdoors, and pine to fresh, spring breeze, and even Hawaiian.
So, which cat litter should you use for your cat? Do cats prefer scented or unscented cat litter?
What does the research say?
The short answer is that it's not clear if cats have a preference for scented or unscented cat litter. One researcher who has conducted a number of studies on cats and litter box behavior is Dr. Jacqueline Neilson, DVM. Dr. Neilson presented the results of one such study at the 2011 Veterinary Behavior Conference.
One relevant study looked at litter use for 35 neutered cats over a four-day period. At the end of the study, the total amount of urine and feces were measured to determine whether cats preferred scented or unscented cat litter. The results? The scented litter was used 134 times, while the unscented cat litter was used 143 times. Dr. Neilson's conclusion was that, in general, cats did not demonstrate a significant preference.
Likewise for individual cats within the study, 16 cats preferred unscented cat litter, 12 preferred scented, and 7 showed no preference at all. This lead Dr. Neilson to conclude there isn't a statistically significant preference for one kind of litter. You can read more about this study here.
Contrasting evidence is found in Dr. Debra Horwitz's 1997 study published in Applied Animal Behavior Science. Dr. Horwitz compared two populations of cats: 100 with a history of housesoiling and 44 with no history of persistent housesoiling. Horwitz did find a correlation between use of scented litter and litter box problems.
Based on these two studies, as well as a number of others, it's not possible to say definitively whether cats prefer scented or unscented cat litter.
A 2010 study by Dr. Neilson, published in the Journal of Veterinary Behavior, might lead us to a slightly different conclusion. In this study, Dr. Neilson examined whether cats show a preference for litter odor control additives, specifically focused on carbon versus baking soda. The abstract of the study can be found here.
The study concluded that cats prefer carbon as an odor-controlling additive compared to baking soda. This result suggests that the question of whether cats prefer scented or unscented cat litter is too simplistic; perhaps there are more nuanced factors at work.
General Fragrance Preferences
There are also studies that focus on which smells cats show a general preference for. Dr. Neilson's work shows up again on this topic; in two studies from 2007 and 2008. Dr. Neilson demonstrated that cats tend to prefer cedar, fish, and bleach aromas and that they tend to avoid citrus and floral scents. Read more about these studies here.
While we might be tempted to draw conclusions about scented cat litter based on these studies, it's important to note that this research wasn't carried out in association with litter box use, but fragrance preferences in general. That said, if you choose to use a scented litter, Dr. Neilson's research might suggest that you avoid litters with citrus and floral fragrances.
Conclusion: Scented vs. Unscented Cat Litter
When faced with unclear and contradictory evidence, what conclusions can we draw? When it comes to scented cat litter vs. unscented cat litter, the question might be part of the problem. Instead of whether the litter has a scent, the determining factor might be what kind of scent that is. And if the litter has a scent, it should be one that the cat prefers—and your cat might have a different set of preferences than your neighbor's cat.
We all want to encourage consistent litter box use and avoid problem behavior, and litter choice is just one part of that calculus. We know (more certainly) that the following conditions must be in place before we begin to blame the litter: Cats prefer clean litter boxes. They want a litter box of adequate size. They want a sufficient number of litter boxes available (usually one more litter box than the number of the cats in the household).
If your cat has no litter box problems, then there's no reason to change your cat litter (which can upset your cat if not switched gradually). If your cat does have litter box problems, after a visit to the vet to rule out medical causes, you may want to try out a different type of litter. Already using unscented cat litter? Perhaps one with an earthy, natural scent will make the difference.