I have a male persian which has been with me for about atleast 8 months and once every month this guy gets a bout of cold every month, when treated by the vet it gets better for about 20 days then the cold is back again, any idea why this happens?
the answer by the vet wasnt staisfying.
its being fed on whiskas and chicken glizzard, beef at times,
any tips etc...

what did you vet say? Does he have a cold or allergies? Bluie has allergies.?

My take on this is that he's not getting a new cold/allergy, he's just not getting over the current one. I believe it sounds more like allergies than a cold and his food should be changed to something more hypoallergenic. This should all be discussed with your vet before making any changes.

Before I make a guess as to what this is, I have a few questions for you:

How is his overall health other than the cold stuff?
What is the vet giving him to get better? Antibiotics? Steroids?
When you say 'cold', what are the symptoms?
Does he have brown wax in his ears?

Unlike the others, I don't think this is an allergy because you say he gets better, then gets worse again. I would say something more like a virus which he is not getting rid of totally. The antibiotics controls the symptoms and once he's off the antibiotics, the symptoms reappear.

So, if you answer my questions, I may be able to help you more.