DEAR DR. DONOHUE: Four months ago I cut my arm. It was a pretty bad cut – about four inches long – and had to be stitched. In the past two weeks, the scar has begun to enlarge, and it seems to keep growing. What’s going on? How do I stop it from getting bigger? – N.N.

ANSWER: You’re describing a keloid, a scar that grows and grows and spreads well beyond the borders of the original injury. The growth might occur long after healing has taken place. These exuberant scars can arise after just about any kind of skin trauma – a cut, a burn, a surgical incision or even after acne. Not only does the keloid scar grow in size, but it also can become tender or painful.

Why keloids form is something that has not been explained. Some people tend to form them, while others don’t. Blacks and Asians are more prone to develop them than are other ethnic groups, but no race or nationality is immune to them.

Collagen, a protein that everyone has heard of, forms the bulk of a scar. In a keloid scar, collagen fibers are arranged in large, irregular bundles, and their production keeps on well after the need for them has gone.

Get back to the doctor who took care of your cut. He or she can advise a number of methods that can often stop keloid progression and shrink it to a more normal size.

One treatment is injection of the keloid with the cortisone drug triamcinolone. Injections are repeated every two to eight weeks. It takes time for this to work, and, truthfully, it doesn’t work for everyone.

Silicone sheeting applied to the keloid can sometimes soften and reduce its size. The sheet is fixed to the scar with a compression wrap like an Ace bandage.

Some surgeons remove the keloid and follow the removal with radiation.

Lasers have had a measure of success in getting rid of these troublesome scars.

DEAR DR. DONOHUE: My daughter is 24 years old. She is planning to get married this coming summer. I can’t remember if she ever got the rubella vaccine. When she was scheduled to get it, her doctor was sick. He subsequently died, and I don’t recall if she ever had the shot.

I know it is important that she have the shot, and I know that it should not be given if a woman is pregnant. How much time has to pass between when the shot is give and when it is safe to become pregnant? – K.H.

ANSWER: Rubella (German measles) is an infection seen infrequently these days thanks to the rubella vaccine. It causes an illness that is usually mild in childhood. Its importance, however, lies in infection during pregnancy, when it can lead to fetal malformations.

The vaccine contains a live virus. Since the rubella virus can be passed to the fetus, pregnant women should not be immunized with it.

Twenty-eight days is a safe interval between the time of immunization and the time of pregnancy.

Your daughter has plenty of opportunity to get the vaccine before her wedding. All unimmunized women of childbearing age should have the vaccine.

There is a blood test that women in your daughter’s predicament can take to tell if they are or are not immune to rubella infection.

DEAR DR. DONOHUE: What causes a ganglion? I have one on my wrist. It doesn’t hurt, but I don’t like the looks of it and would like to get rid of it. How do I do that? – P.P.

ANSWER: A ganglion is a soft bump, usually found on the back of the wrist. It’s a cyst filled with a gelatinous material that has the consistency of uncooked egg whites. It springs from the joint surface.

Ganglions range in size from a pea to a peach pit. Most don’t hurt, and most don’t interfere with wrist motion.

Ganglions sometimes disappear on their own. A doctor can drain one with a needle and syringe, but they often come back after that procedure. The certain way to get rid of one is surgical removal.

DEAR DR. DONOHUE: When I was a kid, I spent summers on my grandparents’ farm. I am 74 now. They talked about lockjaw all the time and told me never to go barefoot in the barn because a cut on the foot there would lead to lockjaw. Now I hear nothing about it. Why? Is it still here? – R.D.

ANSWER: Tetanus is the medical name for lockjaw, and it is still here (United States and Canada), but not in the numbers it once was. You can thank immunizations for that. We see only 50 or so cases every year, but, worldwide, there are more than a million cases.

Tetanus germs are widespread in soil and in the intestinal tracts of animals and humans. Your grandparents warned you about not going barefoot in the barn because animal droppings left a coating of tetanus germs on the barn floor. A puncture wound of the foot would inject a sizeable number of the germs into your body.

Once inside, the germs release a poison that disrupts nerve transmission in the spinal cord. That leads to the muscle spasms that are the hallmark of this illness. The jaw muscles contract so forcibly that they can’t be opened – the reason for the lockjaw name. Back muscles can contract with such violence that a person’s back is arched and the entire body weight rests on the head and heels. During these painful contractions, the patient is conscious but cannot communicate.

There is a message for everyone in the tetanus story. Most tetanus patients in the United States and Canada are people older than 60. The reason is their immunity against the tetanus germ has waned because they received the shot so long ago. All adults should be re-immunized with the tetanus vaccine every 10 years.

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.