If a dog experiences nasal discharge, the best thing to do is consult a veterinarian. The most common cause of a clear discharge from a dog's nose is an allergy. If there is a discharge from just one nostril, it is possible there is something blocking the passage, such as a grass seed. A veterinarian can extract the foreign body.
If the discharge is yellow, green, bad-smelling, or accompanied by coughing, choking or noisy breathing, the cause could be an infection, tumor or polyp. A veterinarian can diagnose the cause and prescribe a treatment. Antibiotics are used to treat bacterial infections. Fungal infections require special drugs. If the cause of the discharge is a polyp or tumor, surgery may be necessary.
If the dog tends to experience nasal discharge after eating, the dog may have a cleft palate or a fistula. Some dogs are born with small nostrils and tend to experience nasal discharge and noisy breathing. A veterinarian can perform a simple surgery to correct this problem.
If the discharge is yellow and the dog has not been vaccinated against it, the dog could have distemper. Distemper is a serious disease that can cause neurological problems and death.
Dogs do not commonly get simple colds that cause the sniffles as people do.