one viral infection after another

If anyone can give a 62 year old lady help to strengthen my immune system, so I don't pick up every cold virus around. I have small grandchildren and of course they have their share of colds, but even if I am in a room with children, like Doctors office, within a day or two I have the start of a cold, sniffles and scratchy throat. I eat healthy and am not to much overweight. Don't recommend echinacha....I took that and broke out in red bumps on my neck. Thanks!