Q. My mother, who lived to be 92, never caught my sniffles in her later years, even though I was her sole caretaker. And now that I'm in my 60s, I notice that my colds are less severe. Is it possible to develop immunity to the common cold?

A. Possibly, to specific kinds of cold, said Dr. Jonathan L. Jacobs, professor of clinical medicine at NewYork-Presbyterian Hospital/Weill Cornell Medical Center.

"The syndrome that we call the common cold can be caused by many different viruses," he said. "After most viral infections, people develop immunity to that specific virus, which can last from a few years to a lifetime."

As immunity to different viruses builds up over time, it decreases the number of viral types that can make one sick, Dr. Jacobs said. But he added, "There are so many viruses that cause colds that complete immunity is very unlikely."

As for the strength of symptoms of colds later in life, "our genes, and the strength of the immune mechanisms that produce many of the symptoms that we associate with the common cold, are also important factors determining how sick we get when exposed to a cold virus," Dr. Jacobs said.

question@nytimes.com

First Published: August 5, 2013, 10:00 p.m.