DEAR DR. ROACH: I am 82 years old and in very good health. I have no major medical issues so far, but I work on my health as I believe in prevention.

During the past eight months, I’ve had three colds, plus COVID-19 for the first time this past November.

I remember the old days when we used to wear camphor necklaces every winter in order to “scare away” viruses.

Before I order one, I want your advice on it.

• N.G.

ANSWER: Camphor is a waxy substance that is derived from the camphor laurel tree.

It is often used topically to relieve pain, but some people use it as a skin rub to relieve congestion. (It’s in Vicks VapoRub and many other products.)

Many people believe in its use as a topical agent, although the evidence supporting its effectiveness is modest.

Wearing bags of camphor to prevent viruses was done during the influenza pandemic of 1918.

It wasn’t effective then and isn’t effective now. I’m surprised that these are still available for sale since they have a significant potential for harm.

Highly concentrated camphor can be poisonous if inhaled and if absorbed through the skin; it can cause vomiting, confusion and seizures.

Some necklaces that are sold as camphor actually contain chlorine dioxide, which is a respiratory irritant that can cause eye irritation.

I am glad that you believe in prevention.

You can prevent yourself from getting sick by not buying these products.

Getting vaccinated every year for the flu, once for respiratory syncytial virus, and as recommended for COVID-19 will actually help to protect you from respiratory viruses.

Viruses may be scary,

but they don’t get scared away.

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.