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.