When a dog is spitting up white foam, it generally means that he is either vomiting or coughing up white foamy matter.  And, he could be doing so as a result of several conditions, some of which are serious while others are of less concern.   Your dog could be spitting up white foam as a result of:

Some of these conditions are more serious than others; some will require more intense treatment than others.

Our canine companions can make some unusual sounds and behave in unusual ways which can be scary to the pet owner.  If your canine companion is spitting up white foam, there could be several conditions/reasons why it is occurring: 

This is a very contagious condition which can be picked up by your pet when he is boarded, has spent time in a shelter or hospital or when he comes into close contact with other canines.  It is an upper respiratory infection which can show up within 10 days of exposure. The most frequent symptoms are a dry, honking cough sometimes accompanied by gagging or coughing up white foam.

Your pet may spit up white foam after eating or exercise because his stomach has filled with air or fluid.  The stomach will become swollen and hard. This is called bloat and can be a very dangerous condition for your pet because, when the stomach fills with air or fluid, it can cause the stomach to rotate, which then traps the food.  It obstructs the veins around the stomach. This condition is unmistakable and dogs get very unwell within a matter of hours.

Sometimes your canine family member will wolf down his dinner or drink a whole bowl of water after exercising and then vomit it back up. Something has probably upset his stomach or he has eaten something which doesn’t agree with his digestive system. You may also find your dog is nauseous, off their food and tired.

Due to the curious nature of most canines, they can pick up fungal organisms as they sniff, scratch or dig into soils which have been contaminated.  This is especially true if the soil contains bird, poultry or bat excrement.  If ingested or inhaled, the fungal organism can cause an infection which is characterized by a harsh cough and a white foam discharge.

Your pet may be rabid, having contracted rabies from an outside source, and may be demonstrating the classic symptom of foaming at the mouth. The foam comes as a result of nerve damage in the mouth and throat which prevents the infected canine from swallowing. Your dog will show other obvious signs of Rabies such as a fever, seizures and fear of water (hydrophobia).

A bacterial or viral lung infection can cause signs including a cough, fever and malaise. The cough can become severe and may be productive in some cases.

Many heart conditions can lead to coughing due to fluid build up in and around the lungs. Oftentimes, a cough will lead to foam being brought back up. 

Certain breeds such as the Bichon Frise and Terriers are more prone to tracheal collapse. It is more commonly seen in middle-aged to older dogs who are overweight. We can see a chronic cough which worsens with exercise. During a coughing fit, it is not uncommon for some foam to be produced.

Parasites within the lungs may lead to signs including a productive, foamy cough and an increased tendency to bleed. Chest x-rays and stool analysis can help us reach a diagnosis.

If the episodes are infrequent and if your pet is otherwise behaving normally, you can likely note the circumstances which preceded them and monitor him for any future episodes.  However, if the episodes become more frequent or if your pet begins to act or behave abnormally or his condition worsens, you should seek medical advice from your veterinary professional as soon as possible.  Depending on how quickly the condition of your pet worsens, seeking that medical advice may need to come in the form of an emergency veterinary facility, as some of the possible causes can be more serious than others.

If the diagnosis is kennel cough, then there may not be any treatment required as the infection generally passes within about 10-14 days on its own, though some veterinary professionals will prescribe antibiotics if a secondary bacterial infection is suspected. Generally, bacterial or viral lung infections can take up to 3 weeks to fully resolve.  Close monitoring may be necessary in these cases as bacterial or viral infections can develop into pneumonia and become very serious very quickly.

Bloat can be a very serious condition and can develop into a life-threatening condition pretty quickly.  If your pet’s stomach is swollen and hard and he is acting like he doesn’t feel good (pacing, refusal to sit or lie down, drooling, unproductive vomiting), get him to an emergency veterinary facility emergently.  The attending vet will need to release the pressure in the stomach which will require removing the fluid or air that has built up in it.  This can be done via a tube insertion into the stomach, or, if the gastric tube is blocked because the stomach is twisted, a needle aspiration will be performed to release the pressure.  If your pet is in shock, he will need to stabilized with IV fluids and electrolytes. Once he is stabilized and the pressure released in the stomach, there will likely be dietary regimens recommended, changes in the feeding schedule and manner in which it is done and exercise routine changes as they relate to feeding time. A twisted stomach requires surgery to resolve.

In the case of kennel cough, vaccination will reduce the opportunity for this upper respiratory infection to inflict your pet.  This is a regulated vaccination and your veterinary professional will guide you as to the frequency of its administration. Of course, Rabies virus must also be routinely vaccinated against.

In the case of bloat, one of the more serious causes of spitting up white foam, there will likely be some lifestyle changes required to reduce the chances of the episode repeating itself.  Your veterinary professional or attending vet will recommend things like:

Ensure your dog's lungworm prevention is up to date.

Monitor any heart murmur that your pet has and consider diagnostic tests such as echocardiograms and chest x-rays if a murmur is detected.

Walk your dog using a harness rather than a neck lead and try to keep them lean and fit, especially if they are a breed prone to tracheal collapse.

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The treatment costs for the various potential causes of spitting up white foam will, of course, be dependent upon the specific diagnosis  For example, kennel cough cost could range from $100 to $300 to treat.  Bloat or stomach dilatation treatment costs could range from $500 to $10,000, depending upon the severity of the bloat and the condition of the canine when seen by the vet.  Rabies costs could range $950 to $2,000 for appropriate treatment.