Why Do Some Dogs Have Jowls? The Science Behind Saggy Dog Cheeks

The Anatomy of Dog Jowls: What's Actually Going On

When you look at a Mastiff's droopy face or a Bloodhound's magnificent flews (the technical term for the pendulous upper lips), you're seeing a combination of specific anatomical structures that differ markedly from tighter-lipped breeds like Greyhounds or Border Collies.

Dog jowls consist of several layered components:

• Labial folds: The skin folds at the corners of the mouth where the upper and lower lips meet. In jowly breeds, these folds are exaggerated and hang well below the mandible.
• Buccal tissue: The cheek tissue that drapes over the lower jaw. This includes skin, subcutaneous fat, and the buccinator muscle, which is relatively less toned in brachycephalic and giant breeds.
• Flews: The pendulous portions of the upper lip, particularly prominent in hound breeds. According to the American Kennel Club's breed standards, flews in Bloodhounds should be long and deep, forming distinct folds.
• Subcutaneous connective tissue: A thicker layer of collagen-rich tissue beneath the skin that gives jowls their characteristic weight and drape.

Evolutionary Origins: Why Nature and Breeders Favored Jowls

However, the traits that breeders selected for do have functional roots worth understanding:

Scent-trapping function (Hound breeds): The long, pendulous flews and jowls of Bloodhounds, Basset Hounds, and Coonhounds serve a mechanical purpose during tracking. As the dog moves with its nose to the ground, the loose skin around the face helps sweep and trap scent particles close to the nasal passages. A 2018 study in the Journal of Veterinary Behavior noted that scent hounds with more pronounced facial folds demonstrated marginally better scent retention at the nares during ground-level tracking, though the primary olfactory advantage comes from the breed's expanded nasal cavity and higher density of olfactory receptors (up to 300 million in Bloodhounds versus approximately 60 million in shorter-nosed breeds).

Protective function (Guardian breeds): In breeds like the Neapolitan Mastiff, Dogue de Bordeaux, and Cane Corso, the heavy facial folds and jowls provided a layer of loose skin that made it difficult for an attacker (animal or human) to get a firm grip. An adversary biting into loose, wrinkled skin would get a mouthful of hide without reaching vital muscle, blood vessels, or bone. This same principle applies to the loose skin seen in breeds like the Shar-Pei across the entire body.

Thermoregulation: The increased surface area of facial skin folds provides modest additional area for heat dissipation through panting and evaporative cooling, though this is a secondary benefit rather than a primary selection driver.

Physiological Mechanisms: How Jowl Tissue Develops

The development of jowls involves several physiological processes that distinguish jowly breeds from their tighter-faced counterparts:

Collagen and elastin composition: The skin in jowly breeds contains a higher ratio of elastin to collagen in the facial dermis, giving the tissue greater stretch and less structural rigidity. This is similar to the genetic variation seen in Shar-Peis, where excessive mucin deposition (hyaluronic acid) in the skin creates characteristic wrinkles. Research from the Merck Veterinary Manual documents how these connective tissue differences manifest differently across breeds.

Gravity and tissue mass: Jowls become more pronounced as dogs age, not because new tissue grows, but because gravity acts on the existing loose tissue over time. The collagen fibers gradually lose tensile strength (a process accelerated in giant breeds that already age faster), and the jowls descend further. This is why a 2-year-old Mastiff may have moderate jowls while an 8-year-old Mastiff has dramatically drooping ones.

Salivary mechanics: Jowls directly affect how dogs manage saliva. The loose lip tissue cannot form a tight seal, which means saliva pools in the buccal folds and escapes more readily. This is why jowly breeds are prolific droolers — it's not that they produce more saliva, but that their anatomy cannot contain it. A Bloodhound can produce the same volume of saliva as a German Shepherd, but the German Shepherd swallows it efficiently while the Bloodhound's loose lips allow it to escape.

Breed Variations: A Comparison of Jowl Types

Not all jowls are created equal. The degree, structure, and care requirements vary significantly across breeds:

Breed	Jowl Type	Severity (1-5)	Primary Function	Drool Level
Bloodhound	Extreme flews + deep labial folds	5	Scent trapping	Very high
English Mastiff	Heavy pendant flews	5	Protection / intimidation	Very high
Saint Bernard	Moderate-deep flews	4	Alpine rescue heritage	High
Dogue de Bordeaux	Thick, corded lip folds	4	Guardian / gripping	High
Basset Hound	Long, low-hanging flews	4	Scent trapping	Moderate-high
Boxer	Moderate upper lip folds	2	Bite work heritage	Moderate
Labrador Retriever	Minimal — slight lip corner looseness	1	Soft-mouth retrieval	Low-moderate

The severity scale above reflects both the amount of visible tissue and the daily care burden for owners. Breeds rated 4-5 require active jowl hygiene routines (detailed in the practical section below), while breeds rated 1-2 typically need only routine face wiping.

Practical Implications: Living With a Jowly Dog

Cost implications: Owning a heavily jowled breed comes with measurable additional costs. Expect to spend $15-30/month on wipes, cloths, and cleaning supplies specifically for facial fold maintenance. If your dog develops lip fold dermatitis (intertrigo), a single veterinary visit with prescribed topical treatment (typically miconazole-chlorhexidine combination) runs $80-200 depending on your region. In severe or recurrent cases, a surgical procedure called lip fold resection (cheiloplasty) may be recommended, costing $800-2,500 per procedure.

Training considerations: Jowly breeds are often among the more stubborn or independently-minded dogs (a trait that correlates with their working heritage rather than their facial anatomy). Use positive reinforcement methods — food motivation is typically excellent in breeds like Basset Hounds and Bloodhounds. Never use aversive tools like prong or shock collars, as these breeds tend to shut down rather than comply under pressure. A front-clip harness (such as the Ruffwear Front Range, $39.95) provides better control for large, powerful jowly breeds without neck strain.

When Jowls Signal a Problem: Medical Red Flags

While jowls themselves are normal breed traits, certain changes in or around the jowl tissue warrant veterinary attention:

Lip fold dermatitis (intertrigo) is the most common medical issue associated with jowls. It occurs when moisture, food debris, and warmth create an anaerobic environment in the skin folds, allowing opportunistic bacteria (commonly Staphylococcus pseudintermedius) and yeast (Malassezia pachydermatis) to proliferate. According to the Merck Veterinary Manual, lip fold pyoderma is particularly prevalent in spaniels, setters, and brachycephalic breeds, though any dog with pronounced lip folds is at risk.

Common Myths About Dog Jowls — Debunked

Myth	Fact
"Jowly dogs drool because they produce too much saliva."	Saliva production is roughly equivalent across breeds of similar size. Jowly breeds drool because their loose lips cannot contain normal saliva volumes. The tissue acts like an overflow channel rather than a seal.
"You can trim or surgically remove jowls for cosmetic reasons."	Lip fold resection (cheiloplasty) is a legitimate veterinary procedure, but ethical veterinarians only perform it to treat recurrent infections or functional impairment — never for cosmetic purposes. The AVMA opposes cosmetic alteration of dogs.
"Jowls mean a dog is lazy or unhealthy."	Jowls are a breed-standard trait determined by genetics, not by diet, exercise, or overall health. A fit, active Bloodhound will have the same jowls as a sedentary one.
"Puppies grow out of their jowls."	Jowls typically become more pronounced with age as skin loses elasticity and gravity takes effect. A Mastiff puppy with moderate jowls will develop heavier ones in adulthood.
"All wrinkly dogs have the same skin issues."	While both Shar-Peis and Mastiffs have excess skin, the underlying mechanisms differ. Shar-Peis have excessive mucin deposition (hyaluronic acid) in the dermis, while Mastiff-type breeds have excess skin with normal mucin levels. Their care protocols and disease risks differ accordingly.

How Are Dog Jowls Different From Human Facial Anatomy?

Humans have relatively tight facial skin with well-defined musculature directly beneath the dermis — our facial expressions are produced by muscles inserting directly into the skin (the mimetic muscles). Dogs share some of these muscles, but the key difference lies in the subcutaneous tissue layer.

In jowly dog breeds, the connection between the skin and the underlying facial muscles is much looser, with a thicker layer of adipose (fat) and connective tissue between them. This allows the skin to move independently of the muscle, creating the characteristic drape. In humans, conditions like Ehlers-Danlos syndrome can produce somewhat analogous skin laxity, but there is no normal human equivalent of canine jowls.

Additionally, the canine orbicularis oris muscle (the sphincter muscle around the mouth) is structured differently from the human version. In dogs, it is less continuous and less capable of forming a tight seal, which is functionally advantageous for panting (their primary cooling mechanism) but means they cannot create suction the way humans can. This anatomical difference is amplified in jowly breeds.

Related Behaviors and Abilities

Dog jowls interact with several other canine behaviors and physical traits worth understanding:

• Drooling and scent communication: Canine saliva contains pheromones and chemical signals. When a jowly dog flings drool (a behavior sometimes called "rope drooling" in Mastiff owners' circles), they are inadvertently distributing scent markers. This connects to the broader canine behavior of scent-marking territory.
• Lip licking as calming signal: All dogs use lip licking as a displacement behavior and calming signal. In jowly breeds, this behavior is more visually obvious because the excess tissue moves more dramatically, making it easier for owners to read their dog's stress or appeasement signals.
• Brachycephalic airway considerations: Many jowly breeds are also brachycephalic (short-nosed), including Boxers, Bulldogs, and Dogue de Bordeaux. The combination of shortened skull structure and excess soft tissue can contribute to brachycephalic obstructive airway syndrome (BOAS), a condition where the soft palate, stenotic nares, and everted laryngeal saccules impede breathing. If your jowly breed also has a short muzzle, monitor for exercise intolerance, noisy breathing, and heat sensitivity.
• Water drinking mechanics: Dogs drink by curling their tongue backward to form a ladle and rapidly withdrawing it to create a column of water. Jowly breeds are less efficient at this process — the loose lip tissue disrupts the water column, leading to more splashing and spillage. A wide, shallow water bowl (such as the stainless steel Petmate Ultra Bowl, 96 oz, $14.99) minimizes mess.