The first principle is that you must not fool yourself--and you are the easiest person to fool.--Richard Feynman, California Institute of Technology physicist and Nobel laureate

I violated Feynman's first principle during a recent book tour. I traveled daily through congested airports, crowded jets and crammed bookstores amid sneezing, coughing, germ-infested multitudes. One day, while squeezed into the sardine section of coach, with the guy behind me obeying the command of the germs in his lungs to go forth and multiply, I cursed myself for having forgotten my Airborne tablets, an orange-flavored effervescent concoction of herbs, antioxidants, electrolytes and amino acids that fizzles into action in a glass of water.

In the logic-tight compartments of my brain, my magic module had trumped my skeptic module. I had not given this product any thought until, much to my chagrin, the host for one of my tour stops, a Menlo Park, Calif., Internet venture capitalist and science blogger named David Cowan, mentioned that recently he had debunked Airborne on his blog (http://whohastimeforthis.blogspot.com). A science-savvy investor, Cowan was quick to spot the clever marketing technique of suggesting that Airborne prevents or cures colds without actually saying so. "Take at the FIRST sign of a cold symptom or before entering crowded environments," the instructions say. Then "repeat every three hours as necessary." In the (really) fine print, however, is this: "These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease."

Even more troublesome is how the company turned a liability into an asset. Most drugs are developed by Big Pharma--Brobdingnagian corporations with vast teams of scientists who have, to date, failed to cure the common cold. Airborne's creator is "Knight-McDowell Labs"--Victoria Knight-McDowell is a schoolteacher and her husband, Rider McDowell, is a scriptwriter. Instead of hiding their lack of credentials, they boast about them on their Web page (www.airbornehealth.com): CREATED BY A SECOND-GRADE SCHOOL TEACHER! "As any confidence artist knows," Cowan explains in his blog, "disclosing unflattering facts up front wins the target's trust." And $100 million in annual sales is all the data the lab needs.

As for real scientific evidence on Airborne, the Web page used to provide a link to "clinical results" (no longer there). When Cowan wrote to the company for the information, he received this reply: "The 2003 trial was a small study conducted for what was then a small company. While it yielded very strong results, we feel that the methodology (protocol) employed is not consistent with our current product usage recommendations. Therefore, we no longer make it available to the public." Why? The company CEO, Elise Donahue, told ABC News: "We found that it confused consumers. Consumers are really not scientifically minded enough to be able to understand a clinical study."

ABC News looked into the clinical trial and discovered that it was conducted by GNG Pharmaceutical Services, "a two-man operation started up just to do the Airborne study. There was no clinic, no scientists and no doctors. The man who ran things said he had lots of clinical trial experience. He added that he had a degree from Indiana University, but the school says he never graduated."

In one final lunge at product verisimilitude (dang it, that zesty taste feels like it works), I consulted Harriet Hall, a retired U.S. Air Force flight surgeon and family physician who studies alternative medicine. Hall looked up Airborne's ingredients in the Natural Medicines Comprehensive Database and found no evidence that any of the ingredients prevents colds. Worse, vitamin A is unsafe in doses greater than 10,000 units a day, and Airborne contains 5,000 units per tablet and recommends five pills a day or more. The only positive finding was for vitamin C, for which some evidence indicates that taking high doses may shorten the duration of cold symptoms by one to one and a half days in some patients. But the large amounts needed may cause side effects. "There's more evidence for chicken soup than for Airborne," Hall told me. "In the absence of any credible double-blind studies to support the claims for Airborne, I'll stick to hand washing."

Chicken soup for the traveler's soul.