A Dog's Penis: Everything You Need To Know

By PetMD Editorial. Reviewed by Brittany Kleszynski, DVM on Nov. 29, 2023
A Newfoundland pup looks out into the snow.

Every part of a dog's body can be injured or affected by disease, including their penis.

Medical issues affecting the penis are uncomfortable, painful, and may be a sign of a potentially serious health condition.

Let’s look at potential medical issues in a dog’s penis, and when you should call to your veterinarian.

What's Normal for a Dog's Penis?

To recognize when something is wrong with your dog’s penis, you need to understand what’s normal.

Most of the time, what you see on the outside of a dog’s penis is the prepuce or sheath—the skin and other tissues that surround the non-erect penis.

The penis itself is covered with a mucous membrane, which makes it appear moist and bright pink or red.

A small amount of yellowish-white or even slightly green-tinged discharge can collect around the opening to a dog’s prepuce, called smegma.

Smegma is a collection of fluid and dead skin cells that helps lubricate a dog’s penis.

It’s a normal secretion in male pups. Some dogs—even when healthy—will produce a large amount of smegma. They will often lick their penis to remove it.

A dog’s penis is rigid even when not erect due to the presence of a bone called the os penis.

A structure called the bulbus glandis is located on either side of the base of a dog’s penis. When a dog becomes aroused, the bulbus glandis swells with blood, creating two visible bumps beneath the skin.

Erections can occur even if a dog is neutered. A full erection may result in the entire engorged penis and bulbus glandis extending outside of the prepuce.

A dog’s erection may last for a few minutes or up to an hour.

Is Your Dog’s Penis Infected?

Pet parents often worry that their dog’s penis is infected. Smegma may be mistaken for pus, a sign of infection.

Drainage from the prepuce and excessive licking are some of the most common symptoms of infection in a dog's penis and/or sheath.

Drainage from the prepuce and excessive licking are some of the most common symptoms of infection in a dog's penis and/or sheath. Because of this, determining what's normal and what's a medical issue may be difficult.

Bring your pup to their vet if:

  • Your dog is licking his penis more than normal

  • Your dog seems uncomfortable or unwell

  • Your dog’s penile discharge has increased in quantity or changed in color

Why Your Dog Is Licking His Penis

A dog will lick his penis to help keep it clean. A pup will also lick his penis because it feels good.

Some dogs will lick or self-stimulate in other ways (mount or hump objects) and get erections, even if they are neutered. Ignore this behavior unless you also notice problems with your dog’s penis or changes in his overall health.

Excessive licking—especially when it’s associated with symptoms like increased drainage, pain, or lethargy—can be a sign of infection, injury, or other conditions affecting your dog’s urinary or reproductive tract.

Call your vet if you notice your pup acting differently.

Why Your Dog Is Bleeding From His Penis

Blood may be seen coming from a dog’s penis because of wounds to the penis or prepuce, conditions affecting the urinary tract (infections, tumors, bladder stones), blood-clotting disorders, and diseases of the prostate gland.

Neutering will cure most cases of BPH in dogs. If a dog’s prostate does not reduce in size following neutering, there may be another underlying issue (such as an infection or tumor) present.

The most common cause of bloody discharge from the penis in an unneutered male dog is benign prostatic hypertrophy (BPH), a non-cancerous enlargement of a dog’s prostate gland associated with exposure to testosterone.

BPH is most commonly found in senior dogs due to cellular changes in their prostate. This occurs as dogs age. This is a result of prolonged exposure to testosterone over time.

Your vet can determine whether your dog has BPH by feeling his prostate gland during a rectal examination. Neutering will cure most cases of BPH in dogs.

If a dog’s prostate does not reduce in size following neutering, there may be another underlying issue (such as an infection or tumor) present.

If your dog has blood coming from his penis, take him to see the vet immediately.

Why Your Dog’s Penis Is Stuck Out

If your dog’s penis becomes erect and visible but then returns to being fully enclosed within the prepuce—and all else seems to be normal—you probably don’t have anything to worry about.

However, dogs will sometimes have persistent erections or can’t retract the penis back into the prepuce, called paraphimosis.

Paraphimosis in dogs can be caused by neurological disorders, trauma, foreign objects within the penile sheath, or anatomical abnormalities.

If your dog’s penis is discolored or the normally moist tissues that cover it are dry, take your dog to the vet immediately.

Difficulties with urination and permanent damage to the penis can occur without immediate treatment.

Why Your Dog’s Penis Is Swollen

Your dog’s penis will become swollen during a normal erection.

If your dog’s swollen penis returns to its normal size within an hour or so—and your pup feels OK otherwise—no veterinary treatment is typically necessary.

However, if your dog’s penis remains enlarged for an extended period—or if you notice any other worrisome symptoms like lethargy, poor appetite, discomfort, or abnormal discharge from the prepuce—you should call your vet for advice.

Medical issues like infections, injuries, and tumors can also make a dog’s penis appear to be swollen.

Is Your Dog's Penis Color Normal?

A dog’s non-erect penis is normally enclosed by his prepuce, which is covered by skin and hair.

When visible, the penis itself is usually pink or red, but can become a darker purple during an erection. The color should return to normal after the erection is over.

A small amount of yellow-white or slightly green-tinged discharge from the end of the prepuce is also normal. If you notice changes to the coloration of your dog’s prepuce, penis, or preputial discharge, take your pup to their vet to rule out any medical problems.

Why There’s Discharge Coming from Your Dog’s Penis

Aside from the normal smegma, other types of discharge or a discharge that comes directly from the penis itself is often associated with a health problem.

Possible diagnoses include:

  • Traumatic injury

  • Foreign material lodged within the prepuce

  • Infection of the urinary or reproductive tract

  • Cancer of the urinary or reproductive tract

  • Urinary tract stones (uroliths)

  • Prostatic disease

  • Blood-clotting disorders

  • Anatomic abnormalities

  • Erectile disorders

Why There’s a Rash on Your Dog’s Penis

The skin-covered prepuce that surrounds a dog’s penis can develop rashes, just like any other area of the body. Because the prepuce touches the ground whenever a dog sits or lies down, it frequently meets irritants, allergens, and insects that may bite.

Parasites and skin infections can also cause rashes on a dog’s prepuce.

Giving your dog a bath using cool water and a gentle soap might help if your dog’s rash developed due to contact with an allergen or irritant.

Some soothing and recommended shampoos for dogs include:

Rashes that are severe, produce significant discomfort, or persist for more than a day or two should be evaluated by your vet.

Why There Are Lumps, Bumps, or Growths on Your Dog’s Penis

It’s normal for lumps to form on either side of the base of a dog’s penis during an erection. These should disappear when the erection ends. Also, it is not unusual to find nipples on the skin on both sides of the penis.

Other lumps, bumps, or growths that persist on or around a dog’s penis are not normal and may be associated with:

  • Injuries

  • Infections

  • The presence of foreign material within the prepuce

  • Inflammation

  • Cysts

  • Tumors

Knowing what's normal for your dog’s penis can help you recognize when something is wrong. Anatomical abnormalities, infections, inflammation, and underlying disease can all affect the health of the penis.

If you have any concerns about your dog’s penis health, visit your veterinarian to discuss your concerns and determine if treatment is needed.

Prompt treatment is beneficial for the overall health of your dog.

Featured Image: Alexandra Draghici/iStock / Getty Images Plus via Getty Images

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