A dog’s vulva can stick out or appear swollen for several reasons, ranging from a normal heat cycle to conditions like vaginal hyperplasia or infection. The most common cause in intact (unspayed) dogs is the estrus cycle, where rising estrogen levels cause the vulva to swell noticeably for one to three weeks. In spayed dogs or cases where the swelling looks unusual, a mass is visible, or your dog seems uncomfortable, something else is likely going on.
Normal Swelling During the Heat Cycle
If your dog hasn’t been spayed, the most likely explanation is that she’s in heat. During proestrus, the first stage of the reproductive cycle, estrogen causes the vulva to swell and produces a bloody vaginal discharge. This stage lasts an average of six to eleven days. The swelling often continues into the next phase, estrus, which lasts another five to nine days (though it can range from one to twenty days). During this time the vulva can look dramatically larger than normal, sometimes alarming owners who haven’t seen it before.
This type of swelling is symmetrical, smooth, and not painful to the touch. Your dog may lick the area more frequently, but she should otherwise act normal. The vulva gradually returns to its usual size once the heat cycle ends. If the swelling doesn’t go down after about three weeks, or if you see tissue actually protruding from the vulvar opening, something beyond a routine heat cycle may be happening.
Vaginal Hyperplasia and Prolapse
Vaginal hyperplasia is the most common reason tissue visibly protrudes from a dog’s vulva. It happens when the vaginal lining becomes swollen and puffy in response to estrogen, then pushes outward through the vulvar lips. It typically appears for the first time between a dog’s first and third heat cycle, though it’s been documented in dogs as young as seven months and as old as eleven years.
There are three stages. In the mildest form, the vaginal floor swells inward without anything visible on the outside. In the second stage, tissue pushes through the vulvar opening and forms a tongue-shaped or pear-shaped mass. In the most severe form, the entire circumference of the vagina prolapses outward, creating a doughnut-shaped mass with a visible opening in the center.
The protruding tissue is pink to reddish, moist, and can look alarming. Difficulty urinating is rare because the urethra sits on the underside of the prolapsed tissue, but the exposed tissue can dry out, crack, or get injured from contact with the ground or from your dog licking at it. The condition tends to recur with each subsequent heat cycle. Spaying is the standard way to prevent it from coming back, since removing the ovaries eliminates the estrogen surges that trigger the swelling. In some cases, the prolapsed tissue needs to be surgically removed before or alongside spaying.
Vaginitis and Infection
Vaginitis, or inflammation of the vaginal canal, can make the vulvar area look puffy, irritated, and more prominent than usual. It occurs in both puppies and adult dogs, spayed or intact. Puppies often have a mild form with small amounts of clear to cloudy sticky discharge and occasional licking of the area, usually without any other symptoms. In adult dogs, the signs tend to be more pronounced.
Common symptoms include vulvar discharge that’s cloudy, white, or yellowish; frequent urination or straining to urinate; scooting along the floor; and persistent licking of the vulva. The licking itself can worsen irritation and make the area look even more swollen. Vaginitis can stem from bacterial infections, urinary tract infections, or anatomical issues that trap moisture around the vulva.
Vaginal Tumors
A mass suddenly protruding from the vulva can also be a tumor. In a retrospective study of 99 vaginal and vulvar tumors in dogs, the most common sign owners noticed was either vulvar discharge or the sudden appearance of a protruding mass. The reassuring finding: about 73% of these tumors were benign, most commonly smooth muscle or fibrous tissue growths. About 17% were malignant. The remaining cases were a type of transmissible tumor spread through direct contact with other dogs.
Tumors are more common in older, intact females. They tend to appear as a firm, rounded mass rather than the smooth, moist tissue seen with hyperplasia. Any new lump protruding from the vulva warrants a veterinary exam, since even benign growths can obstruct urination or become ulcerated.
Recessed Vulva and Skin Fold Issues
Some dogs have what’s called a recessed or hooded vulva, where the vulva sits tucked inward and is surrounded by excess skin folds. This is more common in overweight dogs and certain breeds. The condition itself doesn’t cause the vulva to stick out, but it creates a different problem that owners sometimes confuse with protrusion: the surrounding skin folds trap moisture and bacteria, leading to redness, irritation, pustules, and a foul smell. The resulting inflammation can make the whole area look swollen and abnormal. Dogs with a recessed vulva are also thought to be at higher risk for recurrent urinary tract infections and urinary incontinence, though research suggests this link may be less straightforward than previously believed.
What to Watch For
Some situations call for a prompt vet visit rather than a wait-and-see approach. If tissue is visibly protruding from the vulvar opening, it can dry out and become damaged within hours, especially if your dog is licking or dragging on it. Keeping the exposed tissue clean and moist with a damp cloth while you arrange an appointment helps protect it.
Contact your vet promptly if you notice any of the following alongside vulvar swelling:
- Lethargy, vomiting, or refusal to eat: these can signal a serious internal infection like pyometra, a life-threatening uterine infection in intact dogs
- Straining to urinate or inability to urinate: the protruding tissue or a mass may be blocking the urinary tract
- Foul-smelling or pus-like discharge: this suggests active infection
- Tissue that looks dark, dry, or blackened: this indicates the exposed tissue is losing blood supply and may be dying
- A firm, irregular mass: this could be a tumor requiring biopsy
For intact dogs experiencing vaginal hyperplasia during heat, the swelling often resolves on its own as hormone levels drop, but it will almost certainly return during the next cycle. Spaying between cycles is the most reliable way to stop recurrence permanently. For spayed dogs with unexplained vulvar swelling, infection, anatomical issues, or growths are the most likely explanations, and a veterinary exam is the fastest way to sort out which one you’re dealing with.