Well you can't because dogs do catch colds, but they do catch many other diseases. For that reason you souled give your dog all the necessary vaccines and keep your vets phone on your frig.
Here are two sites that can help you know if your dog is ill.
i'm not sure
By the usual signs of illness; runny eyes and nose, loss of appetite, fever, listlessness. These are some signs for many canine illnesses; some serious some not so.
Members of the canine family rarely get colds. So what may look like a cold to you and I could be more serious. Often dogs will get allergies that look like colds. Canines are prone to allergies but less often to what humans get that is the common cold. Look for the same symptoms that the average person my have wihile battling a cold, but be sure to get vet help as I said before what looks like a cold may be something more seriouse.
Sneezes frequently and has itchy, red eyes. Its based on humans. The actions to human colds are basically the same to dog colds or cat colds. Happy to Help You. -JEN
dogs are pretty much like us they have runny noses , coughs and watery eyes , these are very obvious signs but beware dogs with severe coughs can become ill and get kennel cough, but dogs normally have to be in contact with dogs carrying the kennel infaction . but dont worry most illnesses will run there course naturally .
If its nose is warm and dry
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