cold or flu

Hi all can someone please explain to me why a cold or the flu affects asthma I know it would if you had a chest infection with it but not just with a cold Ive always been told to avoid people with colds and get my flu jab every year. I have had colds in the past and present that has effected my asthma but then again I have had a cold and it not effect my asthma at all. So what is it that determins in a cold if it will effect you. Strange question I know but ive always wondered. Many thanks in advance.

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When you get a cold or the flu, a lot of mucus is produced. This lines your tubes (where you wheezing would start), and so your chest and lungs work harder to breathe. If you have asthma, this can make it a thousand times worse! Think of all that mucus blocking the tubes! Not nice!

Sometimes you can be lucky and your chest/lungs are fine.. so the asthma isn't affected. My asthma always starts before I get a cold!