How not to fight colds

Charlottesville, Va.: In early fall, a few weeks after the start of school, cold viruses wing their way from one young nose to another and thence to families and the workplace, infecting people at three to four times the rate at other times of year. And so the cold season begins and, with it, the relentless sneezing, coughing and sniffling that continue well into winter.

Most of us come down with at least a couple of colds a year; children get up to a dozen. But we all know people who seem never to catch one. What's their secret? Do they have extraordinarily robust immune systems, and the rest of us, pathetically weak ones? You might think this was key, given the number of nutritional supplements, cold remedies and fortified cereals on the market that purport to augment the immune system -- often with the help of vitamins, zinc or ginseng -- and by so doing stave off colds.

But science and experience don't back this up. On the contrary, if you're keen on tamping down your own cold, "boosting" your immunity may be the last thing you want to do.

To understand why this is so requires a bit of knowledge about how colds work. There are more than 200 cold viruses, the most common of which are rhinoviruses (from the Greek "rin-," for "nose"). When you encounter a particular strain, your body eventually produces antibodies to it, which remain on hand to quash that virus the next time you're exposed. But with so many flavors of cold virus circulating, there's always a new one to catch.

From the look of it, these ubiquitous cold bugs are mischief-makers in our bodies. For decades, people thought this was the case -- that the runny nose, sore throat and sneezing we experience with colds resulted from the destructive effects of the virus itself on the innocent cells of our noses and throats. After all, flu viruses work this way; they destroy the cells of our respiratory tract, wreaking havoc in our airways.

But, as medical science has realized over the past few decades, the most prevalent cold viruses in fact do little direct harm to our cells. In one experiment in 1984, researchers at the University of Copenhagen performed biopsies on nasal tissue taken from people suffering severe colds, then did the same after the subjects had recovered. To the scientists' surprise, none of the samples showed any sign of damage to the nasal tissue. Further vindicating the viruses themselves was another study around the same time showing that rhinoviruses infect only a small number of cells lining the nasal passages.

Here was a new insight in cold science: the symptoms are caused not by the virus but by its host -- by the body's inflammatory response. Chemical agents manufactured by our immune system inflame our cells and tissues, causing our nose to run and our throat to swell. The enemy is us.

Indeed, it's possible to create the full storm of cold symptoms with no cold virus at all, but only a potent cocktail of the so-called inflammatory mediators that the body makes itself -- among them, cytokines, kinins, prostaglandins and interleukins, powerful little chemical messengers that cause the blood vessels in the nose to dilate and leak, stimulate the secretion of mucus, activate sneeze and cough reflexes and set off pain in our nerve fibers.

So 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.

It seems counterintuitive, but there it is: 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.

Jennifer Ackerman is the author of "Ah-Choo!: The Uncommon Life of Your Common Cold."