Is cancer caused by risky behavior or bad luck?

DEAR DOCTOR K: I thought cancer was the result of risky behaviors like smoking and spending too much time in the sun. But then I read an article about cancer and bad luck. So which is it -- behaviors or luck?

DEAR READER: I know the article you are referring to, and I wasn't very happy with the way it was presented by the media. Let me start with the bottom line: Cancer is caused by (1) our genes, and by (2) our lifestyle (risky behaviors) and environment. It's not just one or the other. Sometimes genes that we inherit from our parents cause cancer. An example is the BRCA1 gene that causes some cases of breast cancer.

What is malaria and how can I prevent it?

DEAR DOCTOR K: I am traveling abroad in a few weeks. My travel clinic has prescribed antimalarial medication. Can you tell me more about malaria and how to prevent it?

DEAR READER: Malaria is a serious disease caused by the Plasmodium parasite. The parasite is not found today in the United States or Canada, but it is common in areas to which North Americans travel: Africa, Asia, and Central and South America. The U.S. Centers for Disease Control and Prevention estimate that there are over 200 million new cases of malaria each year around the world.

Do we have muscles in our fingers?

DEAR DOCTOR K: A friend told me that we have no muscles in our fingers. Is that true? If so, then how do our fingers do all that they do?

DEAR READER: It is true, but our hands work wonderfully anyway. That's because even though there are no muscles in the fingers, 34 muscles in the palms and forearms make the fingers work. And our fingers perform a remarkable variety of feats, from the practical (opening doors and typing), to conveying information (through sign language or applause), to gathering information about the environment through our sense of touch.

How can you combat MS fatigue?

DEAR DOCTOR K: I have multiple sclerosis. For me, the most debilitating symptom is fatigue. What can I do to feel more energized?

DEAR READER: Multiple sclerosis (MS) is an illness that affects the brain and spinal cord. Normally, an insulating cover called myelin surrounds nerve cells and helps transmit nerve signals. MS is an autoimmune disease in which the immune system attacks the brain and spinal cord. This causes the myelin sheath to become inflamed or damaged, which disrupts or slows nerve impulses.

How does cytomegalovirus affect a pregnancy?

DEAR DOCTOR K: At a recent pregnancy checkup, my doctor said something about cytomegalovirus. What is that, and what does it have to do with pregnancy?

DEAR READER: Cytomegalovirus (CMV) is one of eight members of the family of human herpesviruses. The first two members are the viruses that cause "herpes" sores of the mouth, genitals and other areas. All of the herpesviruses cause a lifelong infection. Once you are infected with CMV, it always remains in your body, generally causing no trouble. Up to 85 percent of adults in the United States have been infected.

Can dogs improve our health?

DEAR DOCTOR K: I'm on the fence about getting a dog. My wife claims that pets -- particularly dogs -- can improve our health. Is that true?

DEAR READER: When I was growing up, there was always a dog in the family. And I mean "in the family": They were a part of the family, often coming with us when we went on errands. Some of my friends never had a pet, so I once asked my mother why we always had a dog. She replied: "Dogs are good for us." I remembered that answer when I got your question.

I’m at risk for osteoporosis, are there any foods I should avoid?

DEAR DOCTOR K: I am at increased risk for osteoporosis. Are there any foods or drinks I should avoid?

DEAR READER: Osteoporosis is a bone-weakening condition that increases your risk of fractures. Though your bones may seem unchanging, they are continuously being broken down and rebuilt. (I've put an illustration of this process below.) Osteoporosis occurs when more bone is broken down than is rebuilt. Osteoporosis is most common in postmenopausal women, but other people are also at risk.

What are some healthy habits to help manage your weight?

DEAR DOCTOR K: One popular book claims that there are "7 habits of highly effective people." Do people who effectively lose weight and keep it off also have habits in common?

DEAR READER: That's a very interesting question -- and I think the answer is "yes." There are certain "habits" that help, but only if you make a long-term commitment to them. Lasting weight loss demands that you transform your eating and exercise habits. But many other choices you make each day can also make a difference. What follows are several habits that can help people achieve -- and maintain -- their target weight.

Can hammertoe be reversed?

DEAR DOCTOR K: Can hammertoe be reversed?

DEAR READER: The four smaller toes of your feet are composed of three small bones, connected by two joints. Hammertoe develops when tendons and ligaments -- the fibrous tissues that connect muscles and bones to one another -- contract. Instead of lying flat, the toes very slowly start to hump up. A bend develops in the joint between the first and second bones; the tip of the toe starts to curl up. The toe resembles a hammer, hence the name.

Is eczema just dry skin?

DEAR DOCTOR K: I took my son to the doctor because he was constantly scratching his legs. The doctor says it's eczema. Is that just a fancy word for dry skin?

DEAR READER: Eczema (also called atopic dermatitis) is more than dry skin. It is an allergic skin condition that can make a child miserable. Treatment can usually help control the condition and ease its symptoms. Eczema can look different in different children. It can be bumpy or scaly, with small or big patches. The amount of redness also varies. Dry, scaling skin usually occurs along with it.