What are some common skin care myths?

DEAR DOCTOR K: I hear and read so much advice about skin care, and I don't know what's true and what's not. Can you address some common myths about skin care?

DEAR READER: You're right to be skeptical. My patients often tell me that they've heard about a way to keep their skin clear and healthy, and often it is simply not true. I'll debunk some of the most common myths I hear:

Is the home-screening test for colon cancer effective?

DEAR DOCTOR K: I heard about a new home test that detects colon cancer. Is it a good alternative to colonoscopy?

DEAR READER: The new test appears to be an advance, but I don't think it's as good as colonoscopy. Particularly for people who are at higher risk for colon cancer, I regard colonoscopy as the best test. Colon (or colorectal) cancer lies in the wall of the colon. It can cause painless bleeding. The amount of blood can be so small ("occult blood") that it isn't visible in the bowel movement, but it can be detected by chemical tests.

What is happening in my body that causes rheumatoid arthritis pain?

DEAR DOCTOR K: I have rheumatoid arthritis. Can you explain what is happening in my body to cause such uncomfortable symptoms?

DEAR READER: Rheumatoid arthritis (RA) is a chronic (long-term) disease. It causes painful and sometimes disabling inflammation of the joints. RA can also affect other tissues in the body, such as the skin, eyes, lungs and blood vessels. RA is an autoimmune disease.

How do I remain motivated to keep up a healthy lifestyle?

DEAR DOCTOR K: Eat right. Don't smoke. Stay active. Can you give me some motivation to keep up these healthy behaviors?

DEAR READER: I think I get your message. This column frequently presents information from scientific studies about healthy lifestyle. But information alone may not be enough to change behavior -- and it's hard to change behavior, particularly when you enjoy it. Information doesn't equal motivation.

During an angioplasty, why is the catheter inserted through the wrist?

DEAR DOCTOR K: I am scheduled to have an angioplasty next week. The doctor plans to insert the catheter through my wrist. Is there some advantage to doing it through the wrist rather than the thigh?

DEAR READER: Angioplasty is a procedure used to open a narrowed or blocked artery. Angioplasties are usually done to open up blocked coronary arteries -- the blood vessels that provide blood to the heart muscle. The blocked coronary arteries lie deep within the chest.

My eyes are affected the most by allergies, what can I do for relief?

DEAR DOCTOR K: I have allergies, and my eyes are affected the most. They're puffy, red and itchy. What can I do?

DEAR READER: Pollens, animal dander, dust mites and mold: The same allergens that cause sneezing and an itchy nose and throat can trigger allergy symptoms that affect your eyes, too. If your eyes are red and itchy, you may also have tearing, mucous discharge and swelling of your conjunctiva (the inside of your eyelid). This constellation of symptoms is known as allergic conjunctivitis. It can be uncomfortable, but it is not a threat to vision.

Are hookahs safe for teens?

DEAR DOCTOR K: You recently wrote about e-cigarettes not being safe for teens. What about hookahs? I don't completely understand what they are. Are they OK for my teen? I think he might be smoking them.

DEAR READER: A hookah is a water pipe that people use to smoke a specially made tobacco. Often the tobacco used in hookahs is flavored, which makes smoking it more attractive to some people. A hookah uses coal to burn the tobacco. This creates either smoke or a vapor that is inhaled through a tube.

How does chemotherapy fight cancer?

DEAR DOCTOR K: My mother was diagnosed with cancer and will soon begin chemotherapy. I'd like to understand how chemotherapy is given, and how it fights cancer.

DEAR READER: Chemotherapy uses drugs that kill cancerous cells, but only injure healthy cells. To understand chemotherapy, you need to understand what cancer is and what is different about cancer cells.

Do I need surgery to remove a nasal polyp?

DEAR DOCTOR K: I think I have a nasal polyp. Will I need to have surgery to remove it?

DEAR READER: A nasal polyp is a noncancerous tumor that grows from the lining of your nose or sinuses, usually in the nasal passages. Nasal polyps often grow in clusters and obstruct airflow in and out of the nose.

Will multiple sclerosis affect my pregnancy?

DEAR DOCTOR K: I have multiple sclerosis. My husband and I would like to have a baby. What do I need to know before I get pregnant?

DEAR READER: Multiple sclerosis (MS) is a disease that affects communication between nerve cells in the brain and spinal cord and the rest of the body. This results in symptoms that may include fatigue, weakness, pain and trouble with movement. In the most common form of the disease, sudden worsening of symptoms (flare-ups or relapses) alternate with symptom-free periods (remissions)