How to use a KONG toy: what the evidence actually supports

A suspension part from a VW bus

The KONG exists because a German Shepherd called Fritz would not stop chewing rocks.

His owner, Joe Markham, ran an auto-repair shop in Denver. While working on a Volkswagen bus he tossed aside a rubber suspension part, and Fritz took an immediate liking to it. Markham spent roughly six years refining the rubber composition, size and shape, consulting rubber specialists in Germany, and started production in 1976. The company has manufactured in Golden, Colorado ever since.

That origin explains the two things people still get wrong about the toy. It was engineered as rubber first and a treat container second, and the shape was never designed to look clever. It was designed to survive a dog.

What the research actually shows

This is where most KONG guides overpromise, so it is worth being precise.

The anchor study. Schipper and colleagues (2008, Applied Animal Behaviour Science) observed eight kennelled dogs given a KONG Extreme stuffed with treats, against a control group of nine dogs observed at the same time with no toy. The dogs with the toy showed more appetitive behaviour, a higher activity level measured by time budgets and behavioural transitions, and lower barking frequency. The authors' own conclusion is careful: a simple feeding enrichment toy is a useful tool for stimulating more varied behaviour, at least in the short term.

What owners report. A 2024 survey in Veterinary Record collected 1,750 usable responses on enrichment feeding. KONGs, chews and activity toys came out as the most-used methods, mainly for delivering treats, presenting meals and occupying dogs during downtime. Owners overwhelmingly perceived mental stimulation as the main benefit. The authors are explicit that this is perception: the design cannot establish causality, and they call for experimental work.

The honest counterpoint. A 2024 study in Scientific Reports tested whether dogs prefer to work for food. Thirty-eight pet dogs were offered a snuffle mat and a plain tray side by side, with equal food in each, across ten trials. Seventy-nine per cent showed some willingness to work for it. Exactly one dog showed a significant preference for the effortful option. Most went to the free tray first.

So the accurate framing is not "dogs would rather earn their food". It is: dogs will happily earn their food, and the earning is what buys you twenty quiet minutes. That is a smaller claim, and it is the one the evidence supports.

You will also see it claimed everywhere that licking releases endorphins and calms dogs. That claim circulates almost exclusively in product marketing and we could not trace it to solid primary research. Prolonged licking clearly occupies a dog. Treat the neurochemistry as unproven.

Pick the line before you pick the size

KONG sells four rubber lines, and the difference is hardness, not decoration.

The Senior line is the one most guides forget, and it matters. An elderly dog with a compromised mouth should not be handed the black one because it is "the tough version".

The size table, with actual numbers

Classic comes in all six sizes. Extreme runs S to XXL, Puppy XS to L, and Senior only S, M and L.

KONG's own safety rule is more useful than the weight bracket: the largest ring of the KONG should be bigger than the back of your dog's mouth. In a multi-dog home, size every toy to the largest dog. Between two sizes, size up.

The filling that solves the calorie problem

Search for KONG recipes and you will find yogurt, banana, pumpkin, cheese and sweet potato layered into something that looks like dessert. Those are fine occasionally. They are a bad default, and the reason is arithmetic.

The standard veterinary guideline is that treats and extras should stay under 10% of daily calorie intake, with 90% or more coming from a complete and balanced food. That 10% is about calories, not about how many treats you hand over, and it counts everything: training rewards, chews, table scraps, KONG fillings.

Fill the toy with your dog's own measured daily ration and the ceiling never enters the picture, because you have added nothing. You have only changed how part of the food is delivered. The 10% budget stays free for the things that actually need it, like the smear of peanut butter you use to make the first sessions easy.

For kibble, add a little water and let it soften. You are not making a paste. You just want the pieces to hold together.

Preparing one, in five steps

1. Measure the day's food. Start from what the dog would eat anyway.
2. Set some aside for training and normal meals.
3. Add a small amount of water and let the kibble soften enough to clump.
4. Load the toy without packing it hard. Early success matters more than difficulty.
5. Freeze it, unless this is the dog's first attempt.

Then work up through four levels rather than starting at the top:

• Level 1 – loose dry kibble that falls out almost immediately.
• Level 2 – softened kibble or wet food, so the dog has to lick and manipulate.
• Level 3 – the same thing frozen, which is where the duration really comes from.
• Level 4 – layered textures, with the higher-value food packed deepest.

The failure mode here is jumping straight to a rock-solid frozen KONG packed tight. A dog that cannot solve it walks away, and rebuilding that interest takes longer than starting easy would have.

Four safety points worth more than any recipe

The small hole is not decorative

The narrow hole at the tip exists to stop a vacuum forming. In a hollow toy sealed at one end, a dog licking deep inside can trap its own tongue by suction, and the harder it pulls the tighter it seals. The tongue then swells, which makes removal difficult without further injury. Veterinary practices report treating tongue lacerations and cutting toys off dogs' tongues and jaws, and there are documented cases of severe injury and death involving single-hole hollow toys.

Practical version: when buying any stuffable hollow toy, especially an unbranded one from a marketplace, confirm it is open at both ends. And never plug the small hole when you stuff it.

The thumbnail test

Veterinary dentists use a simple check: press your thumbnail hard into the chew. If it leaves no dent, the material is hard enough to fracture a tooth. Fractured teeth are among the most common problems veterinary dentists see, and a broken tooth usually means exposed pulp, which then gets infected.

This is what rules out antlers, hooves, bones, hard nylon and rocks, and it is why flexible natural rubber is the safer category. Better still, it is a test you can apply to any toy in the shop, not just this one.

The Extreme is not indestructible

Buyer reviews for the black KONG split hard. Plenty of owners of powerful breeds report it as the only toy surviving months of use. Others report chunks coming off within the hour.

The failure mode is consistent and worth knowing: the rubber is firm enough that a determined dog finds a grip point on the rim and shears pieces off the edge. So when you inspect the toy, check the opening rim first, not the body. Cracks, missing pieces, large tears or chunks gone means replace it.

Multiple dogs means separate rooms

A high-value food toy in shared space is a textbook trigger for resource guarding, and handing out one toy each in the same room does not solve it. Behaviour professionals are consistent on this: separate the dogs physically while they work on food toys.

Xylitol: read the label every time

If you use peanut butter, this is not a footnote.

Xylitol causes a rapid insulin release in dogs and a sharp drop in blood sugar. It can cause seizures, liver failure and death. Symptoms appear quickly: vomiting, muscle weakness, tremors, difficulty walking. If you suspect ingestion, call a vet or a pet poison line immediately.

An FDA veterinarian's guidance is specific to exactly what you are doing here: if you put peanut butter in a hollow chew toy, check the ingredient list first. Peanut butter brands identified as containing xylitol include Go Nuts Co., Krush Nutrition, Nuts 'N More, P28 Foods, No Cow (formerly D's Naturals) and Hank's Protein Plus.

The simplest rule that works without reading every jar: never buy sugar-free peanut butter for a dog.

Washing, and why you want more than one

Rotation is what makes daily use practical: fill, freeze, use, wash, repeat. Three or four toys means one is always ready and you are never assembling one from scratch while the dog waits.

But the washing half is not optional. You are putting food inside porous-feeling rubber and freezing it, and a toy that has held food should be washed after every use.

• All KONG rubber toys are dishwasher safe on the top rack. Skip the heated drying cycle; excess heat damages the rubber.
• Dried-on peanut butter comes out after a soak in warm soapy water and a scrub with a bottle brush or old toothbrush.
• For mould, soak 30 minutes in a vinegar and water solution, then rinse with hot water.
• Air dry completely before storing or refilling. Trapped moisture is how mould starts.

What it will and will not fix

Destructive chewing. It helps, and it is not magic. Dogs chew for boredom, energy, teething, stress and because chewing is inherently rewarding. Giving an appropriate outlet means you are no longer only telling the dog what not to chew. But exercise, training, management and supervision still do most of the work.

Crate training. This is one of its strongest uses. The dog enters the crate and immediately gets something good to work on, which builds the association you want. Supervise with any new toy first so you know how your dog attacks it.

Separation anxiety. Be careful here. A stuffed toy is a management tool, not a treatment. It works for mild cases; a genuinely anxious dog usually will not eat at all once you leave. There is also a less-discussed downside: inside a structured desensitisation programme, a stuffed KONG can interfere with training, because it masks the early stress signals the trainer needs in order to calibrate how long the absences should be. Separation anxiety is a real anxiety disorder, and it generally needs a structured behaviour modification plan, often with a veterinary behaviourist and sometimes medication.

Build it into a routine

Dogs read patterns quickly. Give the toy at consistent moments and its appearance starts doing the work on its own:

• when you start the working day
• when the dog goes into the crate
• after a walk
• during family dinner
• before a short period alone

Over time the toy stops being a distraction and becomes a cue to settle. That predictability is worth more than any filling recipe, and it is the whole reason this toy suits people working from home.

The verdict

The KONG is not remarkable because it does anything revolutionary. It is remarkable because one piece of rubber is simultaneously a chew toy, a food puzzle, a slow feeder, a training reward and a way to buy yourself twenty minutes, and because you can run it on food you already bought.

The evidence supports it as a short-term enrichment tool that increases activity and varied behaviour. It does not support it as a behavioural cure. Bought at the right size and hardness, inspected at the rim, washed after every use and filled with the dog's own ration, it is one of the highest-value purchases in the category.

Buy for size and chew strength first. Worry about recipes later, or never.

PawReviewLab Tip: Before buying any stuffable toy, run two checks in the shop. Press your thumbnail into the rubber and confirm it dents, and hold it up to confirm it is open at both ends. Those two seconds rule out most of the genuinely dangerous products on the shelf.

Sources

• Schipper, L.L., Vinke, C.M., Schilder, M.B.H. & Spruijt, B.M. (2008). The effect of feeding enrichment toys on the behaviour of kennelled dogs. Applied Animal Behaviour Science, 114, 182–195.
• Heys, M. et al. (2024). 'Bowls are boring': Investigating enrichment feeding for pet dogs. Veterinary Record.
• Rothkoff, L., Feng, L. & Byosiere, S.-E. (2024). Domestic pet dogs do not show a preference to contrafreeload, but are willing. Scientific Reports.
• KONG Company. Choosing the Right KONG and How to Clean a KONG.
• AAHA. Don't Chew On This.
• VCA Hospitals. Treats should make up 10% of your pet's daily calories.
• Preventive Vet. Is peanut butter safe for dogs?
• ASPCA. Separation Anxiety.