My name is ***** ***** I’ve been involved professionally with dogs in the health and behavioral fields for over 18 years. It will be my pleasure to work with you today.
There are various reasons for gaggings and coughs including upper respiratory illnesses such as kennel cough and canine influenza as well as bronchitis and inhaled allergies. You can read about these various conditions on the following pages. Many of these, your vet has already ruled out. You can read about bronchitis here.
It’s possible that if sneezing and nasal congestion are present, it can be due to an allergic reaction to an inhaled substance. If this is the case, Benadryl can be given to your dog, the dose is up to 2mg per pound every 8 hours. Treatment would including steroids, and antibiotics as well as an antihistamine. Benadryl is an antihistamine so do not give without your vets approval to ensure he isn't any interaction. You can read about allergies here.
Kennel cough is normally contracted when a dog has been boarded or kenneled or around a large number of dogs such as at a dog show, dog park or pet store. Here is a website with more information on kennel cough. http://www.thepetcenter.com/gen/kenc.html
Canine influenza is now becoming more prevalent and like it sounds it is a canine flu. Here is an excellent site on it.
You will want to monitor your dogs condition looking for colored discharge from the nose or eyes, a productive cough (coughs stuff up), stops eating or lethargy. These are signs of a possible bacterial infection as well and my require antibiotics. If your dog appears to be having a difficult time breathing, you will need to see your Vet as some dogs dog get really sick with canine influenza and need support to recover.
To help your dog breathe easier you can run a NON-medicated humidifier in the room your dog is in, or sit in a steamed up bathroom with your dog to help keep the mucous moving. Robitussin DM at a 1/4 teaspoon per 5 pounds is often used to control the cough. It should only contain dextromethorphan and Guaifenisen. and should NOT contain pseudoephedrine. Dosages can be obtained at this website. However, be sure you check with your vet for drug interactions.
Your vet has ruled out many conditions, so i wouldn't expect it to be a heart or lung condition, but let me give you a site that talks about them.
Your dog could be doing what is called a reverse sneeze or a collapsing trachea. Here is a site on reverse sneezes and one on collapsing tracheas. I think you are likely familiar with these conditions and would likely recognize them.
Allergies or kennel cough seem like likely causes.
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