Do French Bulldogs with longer snouts breathe better? Research says muzzle length matters a lot, but it is not the only factor. Here is what the science shows.

What the research says about muzzle length

Researchers at the Royal Veterinary College measured the faces of 700 dogs of many breeds, then confirmed their findings in 154 flat-faced dogs. They used the craniofacial ratio: muzzle length divided by skull length.[1]

Their conclusion was striking: "BOAS risk increases sharply in a non-linear manner as relative muzzle length shortens. BOAS only occurred in dogs whose muzzles comprised less than half their cranial lengths."[1] In other words, small differences in muzzle length matter most at the very short end, which is where most French Bulldogs sit.

Other features that matter

  • Nostril width. The University of Cambridge reports that French Bulldogs with moderate to severe nostril narrowing are about 20 times more likely to develop BOAS.[2] A separate Cambridge study of 604 Pugs, French Bulldogs and Bulldogs found narrow nostrils linked to BOAS in all three breeds.[3]
  • Neck thickness. Packer's team found thicker neck girths increased BOAS risk.[1] In French Bulldogs, the Cambridge study also linked neck girth relative to chest girth to BOAS, but the authors note that this measurement was not consistent between examiners in the breed.[3]
  • Body weight. Obesity "was found to further increase BOAS risk."[1]

Is a longer-snouted Frenchie still purebred?

It can be. Muzzle length varies within the breed. The AKC standard describes an "extremely short nose" but also calls for "nostrils broad."[4] Some breeders now deliberately select for slightly longer muzzles and open nostrils to improve breathing, while keeping the breed's look and temperament.

Be careful, though. A noticeably long muzzle can also mean a mixed-breed dog. Ask for registration and parent health records either way.

Why a longer snout is not a guarantee

BOAS involves more than the visible nose. It also includes the soft palate, the tissue at the back of the throat and the windpipe. A dog can have a moderate muzzle and still have narrow nostrils or a long soft palate. That is why the Cambridge team recommends a functional assessment: listening to the dog's breathing before and after a three-minute trot.[2]

The reverse is also true. Some very short-faced dogs breathe reasonably well. Function, not looks, is what counts.

How to choose a puppy with better breathing odds

  • Choose parents with open nostrils and a visible muzzle.
  • Ask for the parents' breathing grade from the Respiratory Function Grading Scheme. Grades 0 and I are considered clinically unaffected.[2]
  • Watch both parents breathe at rest and after a short walk.
  • Avoid parents that are overweight or have very thick necks.
  • Keep your own dog lean for life.

Related French Bulldog guides

Sources and references

  1. Packer RMA, Hendricks A, Tivers MS, Burn CC. Impact of Facial Conformation on Canine Health: Brachycephalic Obstructive Airway Syndrome. PLoS ONE. 2015;10(10):e0137496. doi:10.1371/journal.pone.0137496.
  2. University of Cambridge, Department of Veterinary Medicine. Recognition & Diagnosis [Internet]. Cambridge BOAS Research Group; [date unknown] [cited 2026 Nov 3].
  3. Liu NC, Troconis EL, Kalmar L, Price DJ, Wright HE, Adams VJ, et al. Conformational risk factors of brachycephalic obstructive airway syndrome (BOAS) in pugs, French bulldogs, and bulldogs. PLoS ONE. 2017;12(8):e0181928. doi:10.1371/journal.pone.0181928.
  4. American Kennel Club. Official Standard of the French Bulldog [Internet]. AKC; 2018 Apr 10 [cited 2026 Nov 3].

Last reviewed November 3, 2026. Educational information only. This guide does not replace advice from your veterinarian.