Anal gland problems in dogs are most commonly caused by inflammation that blocks the tiny ducts where the glands empty. Allergies, low-fiber diets, soft stool, obesity, and breed anatomy all play a role in why some dogs struggle with their anal sacs while others never have an issue. Understanding the specific trigger behind your dog’s problem is the key to preventing it from coming back.
How Anal Glands Work (and Fail)
Dogs have two small sacs sitting just inside the anus, at roughly the 4 o’clock and 8 o’clock positions. These sacs produce a strong-smelling fluid that normally gets squeezed out in small amounts every time your dog passes a firm stool. It’s how dogs leave their scent signature, which is why they’re so interested in sniffing each other’s rear ends.
Problems start when the ducts that drain these sacs get inflamed or blocked. The fluid inside thickens, the sacs swell, and passing stool becomes painful. If nothing changes, bacteria move in and the situation escalates. The process follows a fairly predictable path: impaction first, then infection, then potentially an abscess that can rupture through the skin near the anus.
Allergies Are the Leading Trigger
The single biggest driver of anal gland disease in dogs is allergies. In a cross-sectional study published in Animals, food allergies accounted for nearly 38% of cases and atopic dermatitis (environmental allergies) accounted for about 30%. The reason comes down to anatomy: the anal sacs are lined with skin tissue, so anything that inflames your dog’s skin also inflames the lining of these sacs.
When allergic inflammation hits the anal sac lining, it triggers excess fluid production and swelling that narrows or seals off the duct opening. The sacs overfill, the secretion thickens, and your dog is suddenly scooting across the carpet or obsessively licking under the tail. If your dog has recurring anal gland issues alongside itchy ears, paw licking, or skin irritation, allergies are a strong suspect. Identifying and managing the underlying allergy, whether through a food elimination trial or environmental allergy treatment, often resolves the anal gland problem along with it.
Soft Stool and Low-Fiber Diets
Firm stool provides the physical pressure that naturally empties the anal sacs during defecation. When stool is consistently soft or loose, it doesn’t apply enough pressure against the glands, and the fluid accumulates instead of being expressed. This is one of the most straightforward causes and one of the easiest to fix.
Diets that lack adequate fiber are a common culprit. Adding both soluble and insoluble fiber to your dog’s diet can firm up stool enough to restore natural expression. Soluble fiber absorbs water and adds bulk, while insoluble fiber adds structure. Plain canned pumpkin (not pie filling) is a popular home option, and there are fiber supplements specifically designed for anal gland support. The change doesn’t need to be dramatic. Even a modest increase in fiber can make a meaningful difference in stool consistency over a few weeks.
Chronic digestive issues like food sensitivities, inflammatory bowel conditions, or frequent diet changes that cause intermittent loose stool can also keep the glands from emptying properly. If your dog has persistent soft stool despite a consistent diet, the gut itself may need attention before the anal gland issue will resolve.
Obesity and Body Condition
Overweight dogs are more prone to anal gland problems for a straightforward mechanical reason: excess fat around the hindquarters changes the anatomy enough that normal muscle contractions during defecation can’t compress the sacs effectively. The glands sit in a pocket of tissue that relies on surrounding muscles to squeeze them. Extra padding interferes with that squeeze.
Obese dogs also tend to be less active, and reduced physical movement further decreases the natural muscle tone around the anal area. Weight loss alone can sometimes eliminate chronic impaction in dogs that have no other underlying cause.
Breed and Body Size
Small and toy breeds are significantly overrepresented in anal gland disease cases. Breeds like Cavalier King Charles Spaniels, Cocker Spaniels, Beagles, Basset Hounds, Chihuahuas, Miniature and Toy Poodles, Lhasa Apsos, and Shih Tzus show up more often with these issues. The likely reasons are a combination of narrower duct openings, proportionally smaller sacs that are harder to empty naturally, and, in some breeds, a genetic predisposition to the allergic skin conditions that drive anal sac inflammation.
That said, any dog of any size can develop anal gland problems. Larger breeds are not immune, especially if allergies or obesity are factors.
How Impaction Progresses to Infection and Abscess
Catching anal gland problems early matters because they escalate in stages, and each stage is harder (and more painful) to treat.
- Impaction: The ducts are blocked and the sacs are overfull. The secretion thickens from its normal thin, brownish consistency to a paste-like texture. Your dog scoots, licks excessively, or strains during bowel movements. At this stage, manual expression by a vet or groomer usually resolves things quickly.
- Infection (sacculitis): Bacteria colonize the stagnant fluid. The secretion turns bloody, and your dog shows more obvious pain, sometimes yelping when sitting or refusing to sit at all. Occasionally, infections develop even without impaction, with discharge visible near the anus.
- Abscess: Untreated infection forms a pocket of pus that creates a painful, red, hot swelling on one or both sides of the anus. If the abscess ruptures on its own, it releases greenish-yellow or bloody pus through a hole in the skin beside the anus. This is painful and messy but actually provides some relief for the dog. It still requires veterinary treatment, typically flushing, antibiotics, and sometimes a drain.
The timeline from impaction to abscess varies, but it can happen within days if bacteria are aggressive. A dog that was just scooting on Monday can have a ruptured abscess by Friday.
Anal Sac Tumors
Rarely, anal gland problems are caused by a tumor called apocrine gland anal sac adenocarcinoma. This type of cancer accounts for about 2% of all skin tumors in dogs and 17% of perianal tumors. It can mimic the symptoms of a simple impaction, which is one reason recurring or one-sided anal gland problems that don’t respond to standard treatment should be evaluated carefully.
Outcomes depend heavily on how early the tumor is caught. Dogs diagnosed before the cancer has spread have a median survival ranging from roughly 2.5 to 3.4 years with treatment. When distant metastases are present at diagnosis, that window drops significantly. Surgery is the primary treatment, and one notable finding from a 2024 study in the Journal of Small Animal Practice is that 20% of dogs with cancer in one anal sac turned out to have cancer in the other sac too, even when pre-surgical workup appeared normal. This has shifted recommendations toward removing both sacs when cancer is found in one.
When Surgical Removal Makes Sense
For dogs with chronic, recurring impaction or infection that doesn’t respond to dietary changes and allergy management, permanent surgical removal of the anal sacs (sacculectomy) is an option. The procedure eliminates the problem entirely since there are no sacs left to become impacted.
Complication rates are relatively low. In one study, intraoperative complications occurred in about 9% of dogs and postoperative complications in about 14%, with surgical site infection being the most common issue after surgery. The anal sacs sit close to the sphincter muscles that control bowel continence, so the surgery requires precision, but fecal incontinence is uncommon when performed by an experienced surgeon.
Preventing Recurrence
Prevention depends on what’s causing the problem in the first place. For most dogs, a combination of approaches works best.
If allergies are the root cause, treating the allergy is the single most effective intervention. A food elimination trial using a novel protein or hydrolyzed diet for 8 to 12 weeks can identify food triggers. Environmental allergies may need ongoing management with medications that reduce skin inflammation.
Dietary fiber adjustments help dogs whose issues stem from soft stool. Consistent stool quality is the goal. A fiber supplement or a food with higher fiber content can maintain the firmness needed for natural gland expression over time.
Keeping your dog at a healthy weight removes the mechanical barrier that prevents natural expression. Regular exercise also supports muscle tone around the anal area. For dogs that still need periodic help, your vet can show you the appropriate schedule for manual expression. Some dogs need it every few weeks, others every few months. Over-expressing glands that don’t need it can actually cause irritation and inflammation, creating the very problem you’re trying to prevent, so this should be based on your dog’s individual pattern rather than done routinely “just in case.”