Surprise! If you get a lot of colds, you're in good shape.
...Susceptibility to cold symptoms is not a sign of a weakened immune system, but quite the opposite. And if you’re looking to quell those symptoms, strengthening your immune system may be counterproductive. It could aggravate the symptoms by amplifying the very inflammatory agents that cause them.
In any case, the supplements, remedies and cereals that claim to strengthen immunity (and thereby protect you from colds) do no such thing. It would be one thing if by some magic they made your body produce antibodies to any particular virus. But they don’t. And though some of these products contain ingredients that have been shown in studies to affect elements of the immune system, there’s scant evidence that they bolster protection against infection by cold viruses. No one knows which immune agents — other than antibodies — accomplish that.
There’s another intriguing paradox here. Studies suggest that about one in four people who get infected with a cold virus don’t get sick. The virus gets into their bodies, and eventually they produce antibodies to it, but they don’t experience symptoms. It may be that people like this are not making the normal amounts of inflammatory agents.
People with more active immune systems may be especially prone to cold symptoms. So getting a cold may be a positive sign that your biochemical defenses are working normally — a glass-half-full view of getting the sniffles. ...NYT