Test subjects with severe colds think they are on the placebo, while those with mild colds guess they have the active drug.

While some researchers are studying positive benefits of the placebo effect, other scientists are noticing its distinct disadvantages. In "Snuffing the Sniffles," veteran cold researcher Ronald Turner shows Alan how test subjects' expectations confound clinical trials.

To test its effectiveness against the common cold, Turner gives volunteers twice-daily doses of a big brown pill. One group receives pills containing an herbal extract being tested for its ability to fend off or shorten a cold. The others look, smell, feel and taste identical, but contain an inert substance - the placebo. Although nobody knows which pill they were given, everyone gets a syringe-full of rhinovirus - one of the causes of the common cold - up the nose. Will those on the active medicine fare better than those given the placebo pill?

Can an herbal extract protect us from the rhinovirus - the commonest cause of the common cold?

Seventy-two hours later, all the volunteers rate the severity of their cold symptoms, and a nasal wash reveals exactly how strongly the virus took hold in each person. Alan asks a few subjects about which pill they think they received. Unsurprisingly, those with the worst colds thought they were on the placebo, while those with the mild colds guessed that they had the active medication.

Later, Turner's analysis shows that it was all in their heads. Turner found no difference in the severity of symptoms between the group that received the herbal extract and the group that received placebo.

Disappointed, Alan - for one - will keep taking his favorite home remedies. And Turner has no problem with that. "If people get some benefit," he tells Alan, "whether it's psychological or mental - that's fine." .

For more on this topic, see the web feature:
The Cold Truth
Coincidental Cures