Should my French Bulldog wear a harness or a collar?
Use a harness, and use it whether or not he pulls. A 2025 study measured intraocular pressure (the pressure inside the eye) and found that in flat-faced dogs a collar raised it even while the dog was standing still, with no tension on the leash; in a harness there was no such effect. The pulling itself is a separate job: stop moving forward when the leash goes tight, pay him for walking beside you, and keep walks short and sniffy rather than long.
In short
The whole chapter in a few lines. Read further only where you want to know why.
A breed summary is only a prejudice about the breed.
You can use prejudices — but get to know your own dog.
It depends on the breeding, the environment, and the dog’s own character. He may have all of the breed’s traits, some of them, or none. Every dog is his own.
1 The measurement that decides this
In 2025, Veterinary Medicine and Science published a study (Bailey et al.; 24 dogs recruited, 20 analyzed) that compared a collar and a harness in flat-faced (brachycephalic) and long-nosed (dolichocephalic) dogs, measuring intraocular pressure — the pressure inside the eye — and respiration rate.
| Condition | Flat-faced dogs | Long-nosed dogs |
|---|---|---|
| Standing still, in a collar | Eye pressure rose | — |
| Exercising in a collar | Eye pressure rose | Eye pressure rose |
| Exercising in a harness | No effect on eye pressure | No effect on eye pressure |
For a breed already prone to eye problems — cherry eye, dry eye, corneal ulcers — that first row is not an abstract number.
The same study measured breathing, and here the result is worth saying out loud because it cuts against the easy story: during exercise, respiration rate rose in flat-faced dogs with both the collar and the harness, with no difference between them.
So the summary is: the harness solves the pressure problem, not the breathing problem. Breathing depends on his anatomy and on how hard the walk is — see BOAS (the breathing disorder of flat-faced breeds).
2 The sentence this study answers
Every owner reading a harness article thinks the same reasonable thought:
“That is for dogs that pull. Mine does not pull.”
Look at the first row of the table again. The pressure was measured while the dog was standing still. Not pulling. Not walking. Standing. In flat-faced dogs, the collar raised eye pressure with no tension on the leash at all.
Which means the recommendation does not depend on your dog’s manners. It depends on the shape of his face. A dog who never pulls once in his life still wears the collar for the entire walk, every day, for years.
The dog in the last section of this page is the clean test of that: he genuinely does not pull, and he still wears a harness.
3 What a collar actually presses with
The introduction of the 2025 study from section 1 collects numbers from earlier research, and they are easier to picture than “pressure” on its own:
- Collars produce contact pressures around 4.58 N/cm² — higher than an ill-fitting saddle on a horse, which is about 3.8 N/cm².
- On a model of a dog’s neck, the lowest collar pressure measured during a firm pull on the leash, 83 kPa, was far above the level shown to cause tissue damage in humans, 4.3 kPa.
- Neck collars have been associated with tracheal collapse, which is seen commonly in small flat-faced breeds.
None of that requires a dog who drags you down the street. It is what the equipment does when it is doing its ordinary job.
4 And here is what is not proven
This is the part most articles leave out, and it is the reason to believe the rest.
A review of dog-worn equipment in Frontiers in Veterinary Science states plainly that claims of collar-related injury from leash-pulling — damage to the thyroid, trachea, jugular veins or carotid arteries — are not supported by published case reports.
So the line we hold is exact:
| Measured | Not documented |
|---|---|
| Contact pressure high enough to matter | Thyroid damage from pulling |
| Eye pressure rising in flat-faced dogs in a collar, at rest | Tracheal, jugular or carotid injury from pulling |
| An association between neck collars and tracheal collapse | A proven cause-and-effect chain from collar to injury |
We recommend a harness because of what has been measured, not because of what circulates online. If the scary version were the only reason, the recommendation would be worth less, not more.
5 Why dogs pull, and why equipment teaches nothing
Our opinion: before any discussion of gear, the reasons are simple:
- It works. Pulling moves him toward what he wants, so every walk pays for it.
- Human walking pace is unbearably slow for a dog.
- Push and he pushes back. Pressure into a body produces pressure in return.
- Arousal feeds itself. A dog who is already over his threshold pulls harder, and pulling raises the arousal further.
Equipment manages the damage. It does not teach him anything. Any article selling a harness as a training solution is selling you something.
And there are two completely different dogs reading this page, which is why so much leash advice feels useless:
| The constant puller | The loose-leash lunger | |
|---|---|---|
| What the walk looks like | Leaning into the leash the whole way | Slack leash by default, then one sudden pull at something |
| Why | It works · human pace · push-back | Arousal, and it has a target |
| What helps | The stop-start mechanism below — slow, boring, effective | Seeing the trigger before he does: distance, an early turn, a change of direction |
If your dog walks beautifully for the whole walk and then takes your arm off once, being told to stop every time the leash tightens is advice for a problem you do not have. Your work is on the seeing-it-first side.
6 What actually works
The equipment. Use a well-fitted harness, front-clip or Y-shaped, with no pressure across the throat and the shoulders free to move. Fit is not a detail: a harness that rubs or slips is the reason people go back to a collar.
Nothing on the neck. For a flat-faced dog, the attachment point never belongs on the neck, and neither does anything that tightens around it when the leash goes tight. That is not a matter of style; it is the same structure that is already his weak point.
The mechanism. When the leash tightens, forward motion stops. That is the whole method, and it is slow and boring on purpose: pulling has to stop producing what pulling is for.
Pay the position. Reward him for being beside you rather than waiting for the absence of pulling. He can only repeat what got paid.
Shorten the trip, not the dog. Our opinion: for this breed, three short walks with plenty of sniffing beat one long march, and heat decides the hours — see heatstroke. How he learns best is its own chapter: how Frenchies learn.
7 Retractable leashes, the trade-off
They get written about as if they were one thing. They are two separate questions, and only one of them belongs to this page.
- The pressure question does not apply. Attached to a harness, a retractable leash puts nothing on the neck. Everything in the sections above is untouched by it.
- The control question is real. Several meters of tape means very little control in the moment you need it, and the handle can be dropped. Where control is the entire point — traffic, a loose dog, a narrow sidewalk — a short leash is a short leash for a reason.
That is the trade-off, without a verdict attached. Choose per situation rather than per product.
8 Spike: our experience
Our stories and opinions on this page are our personal experience with one dog, Spike. One dog is not the measure for every dog — for your dog, your vet decides.
“He does not pull. He wears the harness anyway.”
Spike walks on a slack leash. He goes beside his people or behind them, and he pulls only when he sees something that interests him — interest, not fear, and it is over in a moment.
That makes him the clean test of this page. If the harness were only for dogs that pull, he would not need one. He wears one every walk, because the thing that was measured happens while the dog is standing still.
What he wears is a no-pull harness in size M. His chest girth has never actually been measured; we estimate it at 55–60 cm (22–24 in) from his other proportions, which is why we call it an estimate rather than a number. If you are buying, measure your own dog rather than trusting a breed figure, ours included.
One criterion of ours that gear articles rarely mention: strength. A leash of ours broke once, and since then the first thing we check is whether the thing will hold, before anything about color or price.
And he is the second dog in the table above — the loose-leash lunger. The stop-start method does close to nothing for him, because for fifty minutes there is nothing to work with. What works for this dog is the human noticing the cat, the gate or the other dog first.
Owners Also Ask
Should my French Bulldog wear a harness or a collar?
Use a harness, and use it whether or not he pulls. A 2025 study measured intraocular pressure (the pressure inside the eye) and found that in flat-faced dogs a collar raised it even while the dog was standing still, with no tension on the leash; in a harness there was no such effect. The pulling itself is a separate job: stop moving forward when the leash goes tight, pay him for walking beside you, and keep walks short and sniffy rather than long.
My dog does not pull. Does he still need a harness?
Yes, and that is the most useful part of the 2025 study: the rise in eye pressure was measured in flat-faced dogs that were standing still in a collar, with no tension on the leash. The recommendation follows from the shape of his face, not from his behavior on the walk.
Does a harness fix his breathing on walks?
No. In the same study, respiration rate during exercise rose in flat-faced dogs with both the collar and the harness, and there was no difference between them. The harness removes neck pressure; breathing depends on his anatomy and on how hard the walk is.
Do collars really injure a dog’s neck?
Here we separate two things. What is not proven: claims of thyroid, tracheal, jugular, or carotid injury caused by leash-pulling are not supported by published case reports, and we would rather tell you that than overstate the case. What is measured: contact pressures are high, eye pressure rises in flat-faced dogs wearing a collar, and neck collars have been associated with tracheal collapse.
Is a retractable leash bad?
On a harness it does not put pressure on the neck, so the argument on this page does not apply to it. The real objection is control: several meters of tape gives you little in an emergency, and the handle can be dropped. It is a trade-off by situation, not a verdict on the product.
References
- Bailey ME, Packer MJ, Wills AP (2025). Effect of a Collar and Harness on Intraocular Pressure and Respiration Rate of Brachycephalic and Dolichocephalic Dogs. Veterinary Medicine and Science 11(3):e70384. onlinelibrary.wiley.com
- Bailey ME, Packer MJ, Wills AP (2025) — PubMed Central (PMC). ncbi.nlm.nih.gov
- Health implications of dog-worn equipment: a review of known and alleged physical risks. Frontiers in Veterinary Science. frontiersin.org
- Pauli AM, Bentley E, Diehl KA, Miller PE (2006). Effects of the application of neck pressure by a collar or harness on intraocular pressure in dogs. Journal of the American Animal Hospital Association 42(3):207–211. doi.org
