The editor in chief of the Harvard Health Letter introduces this year's edition of a special issue comprised entirely of "By the way, doctor" letters from readers.

Q. I wash my face very little because I have heard soaps, no matter how mild, dry out the skin. What do you think — what should I wash my face with?

A. Most facial skin is quite sturdy and stands up to repetitive trauma very well. It has many pores and heals quickly and well after injury. But as time passes, the effects of chronic exposure to the environment become evident. The skin thins and becomes less elastic and a bit more porous. Other effects of chronologic aging and cumulative photodamage include freckling, subtle changes in the lines of ...

Q. In addition to a multivitamin, I have been taking vitamin B12 supplements (1,000 mcg) for a few years, hoping to increase my energy. My recent blood profile showed a high level of B12 (1,826 pg/ml). Should I stop taking B12? My energy is about the same.

A. Severe B12 deficiency usually occurs with a condition called pernicious anemia, an uncommon disorder that arises from the inability to absorb the vitamin from food because the stomach does not make enough intrinsic factor, a protein that facilitates B12 absorption.

A more common problem is chronic atrophic gastritis — inflammation of the ...

I'm starting to check my blood pressure at home. When during the day should I do it?

I take a fiber supplement, but have heard that I shouldn't be taking it at the same time as medication. How far apart should I take fiber and medicines such as Plavix and Crestor?

Why are parents not being urged to get their sons vaccinated for HPV?

If coffee constricts blood vessels, why would it help migraine sufferers, since the constriction curtails blood flow, which would seem to cause more pain?

Q. When I attempt to go into the outdoor pool at my beach club, I gasp for breath, get dizzy and light-headed, and have to get out. Several years ago I read an article that some people who are very sensitive to cold water may sustain a heart attack from submersion into cold water. Is this a possibility?

A. Cold temperatures can have important effects on your heart and circulation, so you're smart to be cautious and get out of the water when you start feeling winded and woozy.

Water conducts thermal energy 30 times more efficiently than air, so ...

Thiazide diuretics are often recommended as the first medication to use to control blood pressure, but I've heard that a large study called ALLHAT found an association between thiazide diuretics and diabetes. Is this something to be concerned about?

Do you know anything about the various fancy salts? I've heard that they deliver salty flavor but have a smaller dose of harmful sodium.

Q. My 78-year-old husband has wet macular degeneration. He is being treated with a drug called Avastin. Is that a good choice?

A. Wet macular degeneration is the advanced form of macular degeneration, an eye disease that's the leading cause of vision loss among Americans over age 50. The macula is the center of the retina, the light-sensitive layer of nerve cells (rods and cones) that lines the back of the eye. Wet macular degeneration is caused by abnormal growth of tiny blood vessels into or directly behind the retina; it's "wet" because the new vessels tend to leak fluid ...

Q. I belch a lot and get a feeling of fullness in the upper abdomen. Is this a common condition? What are the causes and cures? I would prefer natural remedies.

A. Belching and feeling full are normal, everyday experiences. So what makes them "excessive"? There's no precise definition. But if you start belching or feeling full more often than you have in the past, or if belching and fullness are causing you distress and discomfort, then I'd consider that excessive and a problem that you should try to solve.

Every time we swallow we take in a little bit ...

I'm in my mid-80s and am infected with H. pylori, the "ulcer bacteria." I don't have any symptoms and have heard that half of everyone over age 60 tests positive for H. pylori and that many people never develop ulcers. Do I need to be treated?

I'm in good health and have a good lipid profile but occasionally have a yearning for brisket or corned beef. I recently read that even one meal heavy in fat could cause atherosclerosis. What do you think?