DEAR DR. DONOHUE: I’m an old retiree who’s had a fingernail fungus problem since I was a teenager. I’ve tried every fungus treatment that drugstores have to offer. Some of them held it in check, but none has been a cure. I don’t want to take anything orally, but I would appreciate any suggestions you can give. – S.N.

ANSWER: Are you sure, beyond the shadow of a doubt, that a fungal nail infection is what you have? Fungal nail infections are more common in older people than in teenagers. Furthermore, it is possible to mistake nail changes from other processes for a fungal infection. Nail trauma, psoriasis, lichen planus and eczema are a few of the conditions that are mistaken for fungal disease. Proof that the nail harbors a fungus is obtained from microscopic examination of the material that accumulates beneath the nail.

A doctor can often do that right in the office. If I were you, that’s where I’d start.

Let me give you some reader suggestions that I have received throughout the years for fungal nail problems: Vicks VapoRub, vinegar soaks and toothpaste applied with a toothbrush.

I have personally tried the first and second without success. As for the third, I don’t believe it works.

Oral medicines, while not a guarantee of success, have a better chance than anything applied directly to the nail, but I respect your desire not to take anything by mouth.

Penlac nail lacquer has a cure rate of about 30 percent. It’s applied directly to the nail.

Before you try it, be aware that it is expensive, and you are committed to a year or more of treatment. Have you ever considered having the nail removed?

Or have you ever considered ignoring it? If the nail hasn’t hurt you in more than 50 years, it’s not likely to cause trouble. Benign neglect is sometimes a good choice for treating such a nail.

DEAR DR. DONOHUE: Perhaps you can explain why flu shots are most strongly recommended for the very young and the elderly when the 1918 Spanish flu killed mostly people in their late teens and into their 30s.

Because of their vigorous immune systems, their bodies responded to the virus by flooding their lungs with fluid, and they literally drowned.

My doctor said the present system is the socially acceptable approach to disbursement of vaccine.

However, the vaccine is plentiful this year. I ask, Why the disconnect between what happened in 1918 and today’s recommendations. – D.C.

ANSWER: The worldwide epidemic of flu in 1918 killed between 21 million and 40 million people. It was one of the greatest plagues mankind has experienced.

In the United States, 549,000 people lost their lives, and the country’s population then was a fraction of what it is today. What you have said is true. In the 1918 epidemic, mortality was highest in previously healthy young adults.

The explanation you give is one that is often offered. Or the virus strain of 1918 might have been one that affected young people in a different way from the usual way viral strains do.

Or it might have been that so many young people were crowded together in 1918 while World War I was still going on, and the close proximity permitted a rampant spread in their ranks.

In truth, no one knows for sure. In those days, immunology wasn’t an exact science, and neither was virology.

I can tell you that since 1918, in every flu outbreak, it’s been mostly older people and young infants who succumb. That’s why recommendations are what they are.

DEAR DR. DONOHUE: I am 74 and have an allergy to latex. Should I be concerned about getting a flu shot? I have gotten them in the past without incident. – J.H.

ANSWER: A latex allergy doesn’t put you at any risk from getting a flu shot. If the one giving the shot has latex gloves on, tell that person of your allergy, and tell him or her not to touch you.

DEAR DR. DONOHUE: I have a lady friend, 80 years old, who has to have a colonoscopy. She has heard that a colonoscopy can bring on dementia. Is this possible? – M.L.

ANSWER: No, colonoscopies do not bring on dementia.

Where in the world did she hear such a thing? Tell her to cross that off the list of things to worry about.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com