Dogs can overact when they feel unwell or when they are just not happy. They will mope and lie around, looking at you for sympathy. The moment you grab the leash or pick up his favourite toy, his attitude will change drastically. This makes it difficult to know when the dog is really ill.
There are some signs that are sure a sure giveaway.
Nasal discharge. This indicates that your dog is suffering some nasal congestion. If it is a thick discharge, the dog might have pneumonia. You might notice the dog is having difficulty breathing or is wheezing. Seek medical attention immediately if you think your dog has a serious nasal or lung congestion.
Vomiting. While dogs will vomit for no apparent reason, there are times when it is serious. Some dogs will eat grass to throw up, although they will also eat grass when they do not feel ill. The grass will cause sufficient irritation to allow the dog to get rid of things like fur balls or small foreign objects in their stomachs. If the vomiting is consistently and violently, consider it to be a sign of serious ill health.
Scratching. Dogs will scratch flea bites or because their skin is dry. It can also indicate that they have parasites such as ticks and lice on the skin. Dry skin can mean that the dog is dehydrated and possibly suffering a more serious illness. Persistent scratching should be checked by a vet.
Diarrhea. Occasionally, dogs can have a reaction to a particular can of food or from something else they have swallowed. If the diarrhea clears itself in a day, chances are it was a temporary condition. If it persists, however, it can mean that your dog has a bowel disorder such as a blockage or internal parasites. Observe the dog to check for limping, a reluctance to walk or refusing food. Any one of these can indicate that your dog might have a renal disorder, like nephritis.
Whiteness in the eyes. If this is present, your dog could have an eye disease or be anaemic. In this case, the mucous membrane of the eyes is paler or white. If the dog bites his chain, owners or others and demonstrates behavior changes, he could have rabies. Protect yourself and others by isolating the dog and staying out of reach to avoid being bitten. Rabies is highly contagious to man and requires painful injections. Rabid dogs cannot be cured.