Why mixing two types of cat litter slashes smells and tracking, according to vets and behaviourists

Thomas Wilkins • December 10, 2025 16:28

You know that resigned little sigh you do when you walk into the hallway and see it again? The faint dusting of litter across the floor, the whiff that says someone has just used the tray, the mental calculation of “do I scoop now or pretend I didn’t notice?” You’ve tried the “low tracking” one, the “odour control” one, the pellets the internet swears by. Your cat has hated at least one of them. The rest are… fine. But your house still smells a bit “cat” by Sunday.

Then a vet or behaviourist casually says during a consult: “Have you tried mixing two types of litter?” It sounds like the sort of thing you’d do when you’ve run out and are cobbling together the last bits from two bags. Yet the more you look into it, the more it turns out this slightly chaotic-sounding hack has real science behind it – for your cat’s brain and nose, and for your floor.

The surprisingly sensible reason experts mix litters

When vets and behaviourists talk about litter problems, they almost never start with “buy this one magic brand”. They start with basics: enough trays, quiet locations, good depth, daily scooping. Then, if you mention smells, tracking or a fussy cat, a pattern crops up in their advice: change the texture, and if needed, combine two.

The logic is simple. Most litters are designed to excel at one thing:

Brilliant clumping but dusty.
Almost no tracking but poor odour control.
Lovely and soft on paws but messy across the house.

Your cat, meanwhile, has a different checklist: “Does this feel safe? Can I dig properly? Does it smell overwhelmingly weird?” When you mix two litters thoughtfully, you can hit more boxes on both lists – yours and theirs – without buying an expensive, heavily perfumed “do it all” formula.

Instead of hunting for a unicorn, you build one.

Why one litter type rarely solves every problem

Cat litters sit on a spectrum, and the trade-offs are pretty consistent.

Clumping clay (bentonite): fantastic for scooping and odour if you’re diligent, often dusty, medium-to-high tracking.
Plant-based pellets (wood, paper, straw): low dust, low tracking, softer impact if kicked out, but can be poor at hiding fresh smells and less diggable.
Fine plant clumping (maize, wheat, soft wood): nicer on paws, clump decently, often lighter – which means they travel farther on fur and between toes.
Silica / crystal: strong odour absorption, low dust, but some cats dislike the feel or noise, and urine tends to pool rather than clump.

You’re usually forced to choose which compromise you can live with. Less tracking, but more smell. Better clumps, but dust clouds. A texture your cat tolerates, but not loves.

Mixing lets you combine strengths:

A top layer that feels good and encourages digging and covering.
A base layer that locks in urine and smells.
A mix of particle sizes that doesn’t stick to paws as easily.

It sounds like alchemy. It’s really just physics and a bit of cat psychology.

What’s going on in your cat’s brain (and nose)

Behaviourists will tell you that a litter tray is not “just a toilet” to a cat. It’s a mini territory patch, full of scent messages. The surface needs to feel safe underfoot, smell familiar, and allow normal instinctive behaviours: sniffing, sniff-marking, scratching, covering.

Two key points vets and behaviourists emphasise:

Texture trumps branding. Many cats care more about how the granules feel between their toes than what the bag claims. Too sharp, too noisy, or too deep and they may hover, rush, or skip the tray entirely.
Smell is information, but not a perfume counter. Cats need to smell something to know a tray is “theirs”, but strong artificial fragrances can read as “chemical stranger” rather than “clean meadow”.

When you only use a very hard, heavy pellet or a strongly scented clumping litter, you’re often asking your cat to tolerate something that suits you more than them. A blended substrate – for example, soft fine litter on top of a more industrial odour-absorbing layer – gives their paws comfort and their brain safety cues, while your nose benefits from better smell control underneath.

How mixing two litters cuts smells and tracking

Here’s what vets and behaviourists are actually seeing in households that mix litters on purpose rather than by accident.

1. Better odour control by layering

Urine sinks down; cats scratch and shuffle the top. If you put a strongly absorbent, clumping or silica-heavy litter at the bottom, and a softer, familiar texture at the top, you get:

Faster capture of urine and ammonia deeper in the tray.
Less “wet patch” left near the surface, so less smell rising when the cat leaves.
Easier scooping, because the bottom layer forms a solid clump rather than a smear.

Your cat still digs and covers in the top layer. You get the benefits of the base layer doing quiet work underneath.

2. Mixed particle sizes mean less tracking

Pure fine-grain litter is pleasant to stand in – and brilliant at travelling down the hallway stuck to fur and claws. Behaviourists note that cats who really enjoy digging in very fine litters often exit with more on their feet.

When you mix in a chunkier pellet or larger granule (wood, paper, or bigger clay), two things happen:

The heavier bits act like tiny “speed bumps” near the tray entrance, knocking excess from paws.
The surface becomes slightly less “fluffy”, so cats are less likely to fling it out with a big back-leg kick.

You still get some tracking – nothing eliminates it entirely – but it’s usually shorter range and easier to sweep.

3. More cats accept the tray

Multi-cat vets see this regularly. One cat prefers soft clay; another tolerates only wood pellets; a third is not fussy but will avoid overpowering smells. A single-type tray forces someone to compromise, which can tip you into “protest wees” on soft furnishings.

A carefully chosen mix:

Feels familiar enough for anxious cats (keep some of their old substrate).
Offers slightly different textures in different trays around the home.
Reduces the risk that a change of brand leads to flat-out refusal.

Think of it less as “messing around with the litter” and more as “offering a richer menu of safe options”.

The combinations that usually work best

Every cat is different, but some mixes come up again and again in vet and behaviourist recommendations.

Mix	Main benefit	Best for
Clumping clay + wood pellets	Strong odour control, lower tracking	Busy, multi-cat homes
Fine plant clumping + wood or paper pellets	Soft on paws, gentler scatter	Indoor-only, sensitive cats
Silica crystals + a thin layer of familiar litter	Big odour reduction, high acceptance	Humans sensitive to smells

A few guiding principles:

Keep one familiar component your cat already uses happily.
Aim for roughly 60–80% “comfort” litter, 20–40% “performance” litter to start.
Adjust ratios slowly over a couple of weeks and watch your cat’s body language.

If your cat starts perching on the edge, hovering, or rushing out without covering, you’ve pushed the mix too far away from their comfort zone.

Step-by-step: how to switch without stressing your cat

Behaviourists strongly warn against overnight, all-at-once changes, especially if your cat already has a history of weeing outside the tray.

Start with a second tray. Keep their usual litter unchanged in one, and experiment with a mixed substrate in another. Most cats will quietly vote with their paws.
Blend, don’t replace. In the “experiment” tray, start with about 80% old litter, 20% new. Mix thoroughly with a scoop.
Watch for three things: how quickly they enter, whether they dig and cover normally, and whether they return to the same tray next time.
Increase slowly. If all is well after 3–5 days, nudge the new component up by another 10–20%. Stop if you see hesitation.
Only retire the old setup once usage is rock solid. Many behaviourists recommend at least two weeks of confident use before removing or radically changing any original trays.

Scooping matters just as much as mixing. Even the best combo will smell if waste sits. For most households, vets suggest:

Scooping solids and clumps at least once daily.
Topping up to maintain a minimum depth of 7–10 cm.
Full change and wash every 2–4 weeks, depending on cat numbers and litter type.

Common mistakes that ruin a good mix

Experts see the same pitfalls crop up:

Too much perfume. Combining two heavily scented litters can create a chemical fog that offends the cat and does little for odour long-term.
Radical texture clashes. Ultra-sharp crystals with very soft sand can feel unstable underfoot, especially for older cats.
Not enough depth. A shallow tray, even with perfect litter, forces urine against the base and sides – hello, lingering smell.
Changing everything at once. New litter, new tray, new location is three simultaneous stressors. If your cat has an accident, you have no idea which one caused it.

Whenever you adjust a mix, change one variable at a time and give it a few days.

When mixing litters really pays off

Vets and behaviourists are most likely to suggest blending litters in these scenarios:

Persistent smell despite daily scooping. A stronger odour-absorbing base layer can change things dramatically without overpowering fragrance.
Chronic tracking on hard floors. Adding chunkier particles creates a more stable surface and reduces how far bits travel.
Multi-cat households. Slightly different mixes in different rooms let each cat gravitate to their preferred texture.
Kittens or seniors. Softer top layers protect delicate joints and tiny paws, while a firmer base keeps the tray hygienic.

If there’s any sign of pain, blood in urine, straining or sudden avoidance of trays, always speak to your vet first. No litter hack fixes a medical issue.

Simple rules to remember before you start mixing

You don’t need a spreadsheet or a lab coat. Just keep a few sentences in mind:

“Keep some of what they know, add a bit of what you need, and change it slowly.”

Prioritise your cat’s comfort over your aesthetic preferences.
Mix one new type at a time, starting in a spare tray.
Make sure the whole setup – depth, size, quiet location – is right, not just the litter.

The right combination will look boring: a tray that smells of very little, and a cat who uses it so calmly you almost forget it’s there.

FAQ:

Is it safe to mix different litters? In most cases, yes, as long as both types are safe for cats individually and you avoid strong chemical additives like deodorising powders not designed for pets. If in doubt, check with your vet, especially for kittens who may nibble litter.

Can I mix clumping and non-clumping litter? You can, but expect weaker clumps. Many people put a primarily clumping litter on the bottom and a thinner layer of non-clumping or pellet on top for comfort and reduced tracking.

Should I avoid scented litters altogether when mixing? Strongly scented litters are more likely to put cats off, especially when combined. If you use fragrance, keep it mild and limit it to one component of the mix.

How fast will smells improve once I change the mix? Some owners notice a difference within a couple of days, once a few wees have been absorbed into the new base layer. Full effect usually appears after a complete litter change cycle.

Does mixing litters replace having enough trays? No. Behaviourists still recommend one tray per cat plus one extra. A brilliant mix in a single overcrowded tray is still a recipe for stress and accidents.