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 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 and the Flu. It is free at

www.peoplespharmacy.com

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Q. My doctor prescribed Soriatane for my psoriasis, but I had to quit taking it. I developed every side effect that was listed in the warnings I got with the medication: Hair loss, blisters and blurred vision, among other things.

After I stopped the Soriatane, I began taking a turmeric capsule twice a day. Within a few weeks, my psoriasis patches were gone. The prescription was very expensive, but the turmeric was not.

A. Soriatane (acitretin) is a powerful chemical cousin to vitamin A, and the side effects resemble those of excess vitamin A. They include dry eyes, dry mouth, hair loss, joint pain, dry skin, nail problems, rash and elevated liver enzymes, among many others. Soriatane can cause birth defects and must be avoided by women who might become pregnant.

Soriatane is for treating severe psoriasis. We hope that you consulted with your physician about stopping the drug.

Turmeric, the yellow spice in curry powder, contains curcumin. This compound is being studied as a possible treatment for autoimmune diseases, including psoriasis (Advances in Experimental Medicine and Biology, Vol. 595, 2007). Although turmeric has fewer apparent side effects than Soriatane, we have heard from several readers that it can increase the effects of the blood thinner Coumadin (warfarin).

Q. Several times, at Mexican or Italian restaurants, I have had a problem with my vocal cords. It becomes extremely difficult to carry on a conversation.

I have found that this condition seems to occur when I eat cilantro, so now I try to avoid it. Once the meal is over, my speaking voice returns to normal. Could cilantro be the culprit? If so, how and why?

A. Allergies to cilantro are not unknown, and could possibly have an effect on your larynx. If you want to be sure, you could ask an allergist to test you. But you are already taking the best action for this problem, which is to avoid cilantro.

Cilantro, also known by the name coriander, is in the same family as anise, caraway and fennel. People with allergies to one of these plants may occasionally develop sensitivities to one or more of the others.

In their column, Joe and Teresa Graedon answer letters from readers. E-mail them via their Web site:

www.PeoplesPharmacy.com

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