A newborn puppy breathing through its mouth is not normal and usually signals that something is blocking or overwhelming its nasal airway. Puppies are obligate nose breathers for the first weeks of life, meaning their bodies are designed to take in air almost exclusively through the nose. When a puppy switches to mouth breathing, it’s typically because it can’t get enough oxygen the usual way. The causes range from simple fluid in the airway (common right after birth) to more serious conditions that need veterinary attention fast.
Why Puppies Breathe Through Their Nose, Not Their Mouth
In newborn puppies, the resistance to airflow through the nose is substantially lower than through the mouth. Their anatomy is built for nasal breathing, and research on neonatal puppies confirms they have real difficulty establishing mouth breathing even when their nasal passages are blocked. This isn’t just a preference. It’s a physical limitation of how their tiny airways work in the first weeks of life.
So when you see a newborn puppy with its mouth open to breathe, it means the puppy is working harder than it should. Something is either obstructing the nose, filling the lungs with fluid, or creating enough oxygen demand that the puppy is resorting to a breathing route its body isn’t well equipped to use.
Normal Breathing in the First Week
Right after birth, a puppy’s breathing is naturally irregular, ranging from 10 to 20 breaths per minute. Over the first seven days, this stabilizes to about 15 to 40 breaths per minute. Some irregularity in the first hours is expected, including brief pauses and occasional shallow breaths, as the lungs clear residual fluid from the womb. A healthy puppy breathes quietly through its nose, with its mouth closed, and its belly and chest rise gently with each breath.
What’s not normal: sustained open-mouth breathing, gasping, wheezing, or visible effort where the puppy’s ribs pull inward with each breath. If the mouth-open breathing lasts more than a few minutes or keeps returning, something else is going on.
Fluid in the Airway After Birth
The most common and least alarming reason is leftover fluid. During delivery, amniotic fluid and mucus can remain in the puppy’s nose and mouth. Normally the mother licks the puppy vigorously to stimulate breathing and clear the airways. If she doesn’t do this, or if the birth was difficult, fluid may linger and partially block the nasal passages, forcing the puppy to open its mouth.
You can help by gently suctioning the nostrils with a small bulb syringe. Squeeze the bulb first, then place the tip gently at the opening of one nostril, and release the bulb so it draws mucus out. Squeeze the contents onto a tissue and repeat on the other side. Hold the puppy with its head slightly tilted downward so gravity helps fluid drain. If the mucus is thick and won’t come out easily, a drop of sterile saline at each nostril can thin it.
After clearing the airway, most puppies will resume quiet nose breathing within a few minutes. If they don’t, the cause is likely something beyond simple fluid.
Overheating
Puppies can’t regulate their own body temperature well in the first two weeks. If the whelping area is too warm, a puppy may open its mouth in an attempt to cool down, similar to panting in adult dogs. This is easy to rule out: check that the ambient temperature in the nesting area is around 85 to 90°F (29 to 32°C) for the first week. If it’s significantly higher, or if a heat lamp is too close, move the heat source back and see if the breathing normalizes.
Cleft Palate
A cleft palate is a gap in the roof of the mouth that connects the oral and nasal cavities. It’s one of the more common birth defects in puppies, especially in brachycephalic (flat-faced) breeds. The opening prevents the puppy from creating the seal it needs to nurse effectively and can also interfere with breathing by allowing milk or air to pass between the mouth and nose in abnormal ways.
Signs beyond open-mouth breathing include difficulty latching onto the mother, milk bubbling from the nose during or after nursing, coughing or gagging during feeding, and failure to gain weight. You can often see a cleft palate by gently opening the puppy’s mouth and looking at the roof. If you spot a gap or slit, the puppy will need veterinary evaluation. Severe clefts require surgical repair, but the puppy typically needs to grow for several weeks before surgery is safe, so tube feeding or bottle feeding with careful technique becomes necessary in the meantime.
Aspiration Pneumonia
When milk or fluid enters the lungs instead of the stomach, it causes aspiration pneumonia. This happens most often in puppies with cleft palates, puppies that are bottle-fed with too much pressure or at the wrong angle, or puppies that are too weak to coordinate swallowing properly. The inhaled fluid triggers inflammation and infection in the lungs, making it progressively harder to breathe.
A puppy with aspiration pneumonia may breathe with its mouth open, sound congested or “crackly,” become increasingly lethargic, refuse to nurse, and feel warmer than its littermates. The condition worsens quickly in neonates. Without treatment, the infection spreads and oxygen levels drop. If you suspect a puppy has inhaled milk (you saw it choking or sputtering during feeding and it hasn’t recovered), this warrants an urgent vet visit.
Fading Puppy Syndrome
Fading puppy syndrome is a catch-all term for newborns that seem healthy at birth but progressively weaken and die, usually within the first one to two weeks. The causes vary and include infections, inadequate nutrition, low birth weight, and immature lung development. One proposed mechanism involves a cycle where a marginally oxygen-deprived puppy doesn’t breathe deeply enough to stimulate the production of surfactant, the substance that keeps the lungs’ tiny air sacs from collapsing. Without enough surfactant, the puppy becomes more oxygen-deprived, stops nursing, loses body heat, and continues to decline.
Respiratory distress, including open-mouth breathing and labored effort, is a key warning sign. Other signs include diarrhea, progressive weakness, inability to nurse, crying that becomes weaker over time, and feeling cold to the touch. Fading puppy syndrome can progress to fatal dehydration or organ failure. The timeline is often fast: a puppy that seemed “a little off” in the morning can be in crisis by evening.
Heart Defects
Congenital heart problems, while less common, can cause labored breathing in neonatal puppies. Defects like patent ductus arteriosus (a blood vessel that should close after birth but doesn’t) or holes between the heart’s chambers can lead to fluid backing up into the lungs. Published veterinary case reports describe puppies as young as 12 to 15 days old presenting with labored breathing and poor nursing due to pulmonary fluid buildup from these defects.
A puppy with a heart defect may breathe with its mouth open, tire quickly during nursing, grow more slowly than littermates, and show a bluish or purplish tinge to its gums or tongue. Heart defects are diagnosed by a veterinarian using imaging, and treatment depends on the specific defect.
How to Check if It’s an Emergency
The single fastest way to gauge severity is gum color. Gently lift the puppy’s lip and look at the gums and tongue. Healthy gums are pink. If the gums or tongue appear blue, purple, grey, or white, the puppy is not getting enough oxygen and needs emergency veterinary care immediately. This color change, called cyanosis, indicates the situation has already become critical.
Other signs that push this from “watch closely” to “go to the vet now” include:
- Gasping or fish-mouthing: rhythmic opening and closing of the mouth with minimal air exchange
- Rib retraction: visible pulling inward of the skin between the ribs with each breath
- Silence after crying: a puppy that was vocal but has gone quiet and limp
- Cold body temperature: the puppy feels noticeably cooler than its littermates
- Refusal to nurse for more than two hours
Newborn puppies decline fast. Their small body size means they have very little reserve of energy, hydration, or oxygen. A puppy showing open-mouth breathing that doesn’t resolve within minutes after clearing the airway and adjusting the temperature should be evaluated by a vet the same day. If gum color changes or the puppy becomes limp, treat it as a true emergency.