DEAR DR. DONOHUE: In a recent column, you stated that cold sores are the result of oral sex. How soon does a cold sore appear after you’re infected? How long does the sore stay? What is the remedy? – Anon.

ANSWER: Let’s go over the herpes virus story to straighten the picture.

Herpes simplex virus type 1 (HSV-1) causes most cold sores. Herpes simplex virus type 2 (HSV-2) causes most genital herpes infections.

HSV-1 – the cold sore virus – is usually acquired in childhood and not through sexual contact. Its incubation period, the time from the virus landing on the lips to the time of the sore’s appearance, is between two and 12 days. It begins as a red patch with small blisters on it. Eventually the blisters break to form a sore that lasts 10 days to two weeks. Not all infections cause an outbreak of a cold sore. Quite a few people have no symptoms from the infection, but they, like the ones who do have an outbreak, remain infected for life. The virus travels up a nerve to its home and stays there from that point on. From time to time, in some but not all, the virus springs into action and travels down the nerve to generate a new cold sore. Most adults have antibodies in their blood – proof of prior infection.

In a very limited number of instances, herpes simplex virus 2 – the cause of genital infections – can be transferred to the lips through oral sex. The result is a cold sore that has the same appearance as the cold sore of HSV-1.

Remedies for both herpes infections include acyclovir, which is available as a tablet or an ointment. Famvir and Valtrex, both oral medicines, are two other herpes fighters.

Readers have a great devotion to lysine as treatment for cold sores, not genital infections. It’s an amino acid and can be found on the shelves of all drugstores. I can’t testify to its effectiveness, but I can testify to people’s praise of it. It can’t hurt.

The booklet on herpes genital infection goes into the herpes story in greater depth. Readers can obtain a copy by writing: Dr. Donohue – No. 1202, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6.75 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: I recently woke with an ankle that felt irritated. I worked that day. By the end of the working day, I needed help in finishing my job. My ankle and foot had swollen very badly. That night I woke with a soaking sweat, and my foot and ankle were killing me. They were twice the size of the other foot and were red and throbbing. I drove myself to the ER, and they put me on an IV antibiotic. I was somewhat better by the morning. They said I had cellulitis. What is it? – M.D.

ANSWER: Cellulitis is an infection of skin cells and the tissues directly beneath the skin. It usually happens on the legs, and most often it’s caused by the Staph or Strep bacterium.

The bacteria enter the skin through a cut, a puncture wound or a boil. The break in the skin can be so small that a person isn’t aware of it. Once the infection gets a start, it spreads rapidly, turning the skin red, causing the leg to swell and producing severe pain. Infected people often experience fever and chills.

Antibiotics have to be given quickly to stop the infection’s advance. Left alone, it can get into the blood, with grave consequences.

DEAR DR. DONOHUE: I am 82 and active. I read that there is an inoculation to prevent shingles. Is this true? – H.S.

DEAR DR. DONOHUE: I am 74. I had chickenpox at 20. Should I get the shingles shot? – B.B.

ANSWER: Everyone 60 and older should get the shingles vaccine Zostavax. It works.

The vaccine has to be kept at low temperatures, and some doctors’ offices don’t have the resources to store it at those temperatures. The family doctor can, however, tell you where it’s available in your area.

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