DEAR DR. ROACH: What do you know about copper killing the cold virus? I’m of the opinion that if it sounds too good to be true, it probably is. Yet, there is a copper product on the market that says it kills the cold virus on contact. Many people have claimed it is effective. Are all these reviews fake? If preventing a cold was this easy, wouldn’t everyone know about it? — J.

ANSWER: Copper does have antimicrobial properties. Bacteria will die on contact with pure metallic copper. The amount of time needed ranges from a few minutes for some Staphylococcal species to 5-15 days for the bacteria that causes tuberculosis. Viruses, which are somewhere between alive and not alive, being only able to replicate within a cell, can be destroyed by copper as well. For the influenza virus, 99.99% can be destroyed by keeping it in contact with metallic copper for six hours.

Unfortunately, cold viruses and flu viruses can be inhaled and then taken up by cells, allowing them to replicate and further infect a person. There is simply no way a piece of copper can prevent infection by viruses when rubbed on the nose. That’s why there are no clinical trials showing the copper to be effective: It isn’t.

I don’t think most of the people responding are fake. The power of believing that something is working is incredible. I suspect many of the people writing testimonials are also not being exposed often to cold viruses.

There is no way to prevent a cold with 100% certainty. Handwashing and avoiding sick people remain the best treatments we have.

DEAR DR. ROACH: I have been diagnosed with granuloma annulare by two dermatologists. The rashes are on my hands, arms, legs and the back of my neck — and they’re spreading. Online research tells me that the cause is unknown and therefore there seems to be no cure. I have used two prescribed steroidal creams and taken high-dose niacin with no success. What can you tell me about the prospects of a cure? — K.M.

ANSWER: Granuloma annulare indeed has no known cause. Infection has been long suspected, but many attempts to identify an infectious agent have been unsuccessful. It varies quite a bit in appearance but most commonly looks like a ring, anywhere between skin color to dark red. It is sometimes itchy. The kind it sounds like you have, called the generalized form, affecting many areas of the body, happens more commonly in people over 30; children and adults into their 20s tend to have the limited form. It is more common in women.

I refer cases to a dermatologist, and my patients often have had success with injection of steroids. It is more effective than steroid creams or ointments. Some people require systemic treatments, such as hydroxychloroquine (Plaquenil). The vitamin A derivative isotretinoin, most commonly used for acne, is also sometimes used.

GA can disappear as mysteriously as it comes. About 75% of people will be free from disease in five years.

* * *

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.