Clinical signs of KC include coughing, gagging, and retching. Buddy had this once and it sounds awful! But fortunately it's not as bad as it sounds. Vaccination is available to decrease the incidence of KC. However, vaccinated pets can still get kennel cough as there are many causes of kennel cough and the vaccine only protects against the 2 most common infectious agents. Most holistic vets will tell you to skip the vaccine - can cause more harm than good.
You really just need to let it run it's course and keep him from other dogs. Vitamins AC & E can help support the immune system as well as herbs such asastragalus, Echinacea, garlic and ginger.
Buddy's cough was so bad sometimes it sounded like he was going to gag. We used a natural syrup called
Apitherapy Honey Wild Cherry Bark Syrup by Honey Gardens (from the health food store) to help as an expectorant and with the cough. It contained raw honey, apple cider vinegar, wild cherry bark, ginger root, licorice, and other things that really helped him a lot.
Hope this helps. Sorry you have to go through it though.