DEAR DR. DONOHUE: I am a 77-year-old woman in good health. Twelve years ago I had an Arthus reaction to tetanus vaccine. There was considerable swelling at the injection site. I also had chills and fever, ached all over and just plain felt miserable. I understand that it is wise to have a tetanus booster every 10 years. Is it safe for me to have this shot? — A.O.

ANSWER: An Arthus reaction is a severe allergic reaction. The injection site turns red and swells, and small blood vessels in the area break and bleed. The skin eventually dies to create an open sore. The reaction begins shortly after the injection.

The guidelines for revaccination for tetanus say: “Defer revaccination of a person with a history of Arthus-type hypersensitivity reaction from a previous dose of tetanus vaccine until at least 10 years have elapsed since the last dose.” Ten years have elapsed since you had the shot, but the words “at least 10 years” make me reluctant to advise getting revaccinated with it. “At least” implies to me that a longer interval is better. Furthermore, you had signs that the reaction was widespread. You had fever, chills and ached all over. This is more than an Arthus reaction. I wonder if the benefits of getting the shot again outweigh the risks of another reaction. In 2007, 28 cases of tetanus were recorded in the United States. The likelihood of you getting the illness is small.

Tetanus (lockjaw) is a dreadful illness. Muscles spasms of such violent proportions leave people in horrendous pain. It can be not only extremely painful but also lethal. Older people are at risk, because their immunity has waned. Ten-year revaccination is recommended for all. In your case, I wouldn’t get another shot unless an allergist feels it is safe. I would urge you to meticulously clean all puncture wounds that occurred in situations where soil or dirt could enter the wound, the usual setting for a tetanus infection.

DEAR DR. DONOHUE: Why, after 15 years of having stopped smoking, has emphysema suddenly appeared? After no symptoms, it suddenly becomes a part of your life. — C.C.

ANSWER: For how many years did this person smoke, and how many cigarettes a day were smoked? It can take time for symptoms of emphysema — breathlessness on slight exertion — to show up even though the damage was done years in the past. Not all damaged lung tissue heals. Add to that damage the emphysema that comes to everyone from aging. Nonsmokers rarely show symptoms of age-related emphysema. Prior smokers often do. I can say that those 15 years of not smoking greatly reduced the risk of coming down with more serious symptoms sooner. What could have been a crippling illness is unlikely to be so.

The booklet on chronic obstructive pulmonary disease (emphysema and chronic bronchitis) explains both in detail. To obtain a copy, write: Dr. Donohue — No. 601, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6. Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: I had a colonoscopy a few days ago and was told I had a serrated adenoma. Is this a health threat? I didn’t understand the explanation too well, and am a bit concerned. I am a male in my early 80s and otherwise in reasonably good health. — A.P.

ANSWER: An adenoma is a colon polyp with the potential of becoming colon cancer. Removal of such polyps greatly decreases the cancer risk. “Serrated” indicates that the exterior of the polyp has small projections, like the teeth on a saw.

The microscopic exam of an adenoma furnishes solid information on its cancer potential. Changes called dysplasia are seen with microscope lenses. The greater the dysplasia is, the more chance exists for the adenoma to be cancerous. Size is another important prognostic sign. Cancer is rarely found in an adenoma smaller than 1 cm (0.4 inch).

Serrated adenomas rarely have dysplastic changes. Your doctor can confirm this for you.

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.