Q. There is a message circulating on the Web about putting an unpeeled onion in a room to attract flu viruses. Apparently this is supposed to protect people from catching the flu. Is there any truth here?
A. There is no reason to think that onions could attract flu viruses out of the air the way the way a flame attracts moths. Viruses are not self-propelled. Though they get into the air when a person with flu coughs or sneezes, they have no more control over where they go than dust particles do.
The belief that onions have power against respiratory infections goes back a long, long way. The first printed reference cited on snopes.com, which examines urban legends and rumors, dates from 1900 and refers to “an old custom,” so putting an onion in a room to fight infection was already an old and possibly untraceable folk practice by then.
Washing hands frequently and avoiding those who have the flu are better precautions than putting onions around the house. For more information on fighting influenza, we offer our Guide to Colds, Coughs & the Flu.