Dogs have anal glands because they act as powerful scent-marking organs that help with communication, territory marking, and possibly lubricating poop as it passes out of the body. Even though pet dogs no longer need them as much as wild canids did, the basic anatomy and function have stayed with them.

Quick Scoop

Think of anal glands (also called anal sacs) as two tiny scent bags sitting at about the 4 and 8 o’clock positions just inside your dog’s anus. Each sac holds a very strong-smelling, fishy, unique “ID fluid” that other dogs can read like a personal profile.

When a dog poops and the stool is firm enough, it presses on these sacs and squeezes a small amount of that scent out onto the feces. This leaves a clear chemical message behind, which is why dogs are so obsessed with sniffing each other’s butts and fresh poop on walks.

Why Dogs Have Anal Glands (The Evolution Angle)

In the wild, strong scent is incredibly useful, and anal glands likely evolved for several related reasons:

  • Territory marking: The fluid coats the stool and nearby ground, helping mark where a dog has been and who it is.
  • Social ID card: The secretions contain pheromones that can signal sex, reproductive status, health, and individual identity to other animals.
  • Extra alarm system: Many dogs involuntarily “express” their glands when suddenly scared or stressed, releasing a blast of powerful scent that may have originally functioned as a fear or alarm signal.
  • Possible lubrication: The oily fluid may slightly lubricate the anus and stool, making defecation smoother, especially for very dry feces.

Modern household dogs do not truly need this system in the same way wild canids once did, but evolution tends to keep structures that aren’t actively harmful, so the glands remain.

What Can Go Wrong With Anal Glands

Because these glands are still there but not always used “perfectly,” they can cause issues:

  • Blocked or impacted glands: If the sacs don’t empty properly—often because stools are too soft, the ducts are narrow, or the dog is overweight—the fluid thickens and the sacs swell.
  • Infection and abscess: Stagnant material lets bacteria build up, leading to painful infection and sometimes abscesses that can even rupture next to the anus.
  • Ongoing trouble in some dogs: Chronic soft stool, low-fiber diets, allergies, skin disease, and small-breed genetics can all make recurrent anal gland problems more likely.

Common signs something is wrong include:

  • Scooting (dragging the butt along the floor)
  • Licking or biting around the anus
  • A sudden, foul, fishy smell
  • Straining to poop or reluctance to sit down

If any of that shows up, a vet visit is important, because untreated impaction can quickly become very painful.

Do Dogs Need Their Anal Glands Removed?

Most dogs will go their whole lives without needing anything more than the natural expression that happens when they poop. In a small group of unlucky dogs with repeated, severe disease (especially abscesses or tumors), vets may recommend surgical removal, but this is considered a last resort because surgery can damage the anal sphincter and cause long-term issues like fecal incontinence.

For many dogs with minor or occasional problems, vets focus instead on:

  • Manually expressing the glands when needed
  • Adjusting diet and fiber to firm up stool
  • Managing allergies or skin disease that may be contributing to irritation and chronic inflammation

TL;DR: Dogs have anal glands because they evolved as scent-marking and communication organs that coat the poop with a powerful, individual smell—and although that’s less essential for modern pets, the anatomy is still there, which is why those smelly little sacs sometimes cause trouble. Information gathered from public forums or data available on the internet and portrayed here.