Syncope is the medical term for fainting due to a lack of oxygen and nutrients to the brain. Fainting spells in dogs, as in humans, can be scary to witness. Signs of syncope are sudden collapse and unresponsiveness. Some dogs may cough or vomit before fainting and may even urinate or defecate.
Fainting can happen for a number of reasons. Some breeds of dogs are more prone to fainting due to physical exertion, such as the flat-faced dogs like pugs and bulldogs, because the breeds have a short nose and airways which can restrict the amount of oxygen they breathe in. The good news is that many fainting episodes are not linked to any serious underlying diseases. Fainting episodes are not painful or distressing to the dogs and they tend to recover quickly after. However, any dog that experiences a fainting episode should be taken to the vet to rule out any serious underlying causes. Some of the more concerning health conditions that may cause fainting are heart disease, bleeding, and other respiratory conditions to name a few, which may have a worse prognosis and may require long-term treatment.
Dogs may also collapse for other reasons besides syncope or may be suffering a seizure which can be confused with a syncopal episode so it is imperative that you take your dog to the vet after any collapse so that they can be properly diagnosed and treated.