Will giving my baby peanut products increase or decrease his risk for a peanut allergy?

DEAR DOCTOR K: My baby has an egg allergy. His doctor says this increases his risk of developing a peanut allergy. She recommends avoiding peanut products for now. But another doctor gave me the opposite advice. What should I do?

DEAR READER: If your child has a food allergy, you may well agonize over the safety of his every meal and snack. And no wonder. Food allergies can cause severe -- even deadly -- allergic reactions. Peanut allergies can cause bad rashes, severe difficulty breathing, a dangerous drop in blood pressure and other dangerous results. But a study recently published in The New England Journal of Medicine offers some hope for parents of infants who may be headed toward a peanut allergy. That hope is peanuts.

Why should I increase my postassium intake if I have high blood pressure?

DEAR DOCTOR K: I have high blood pressure. As I expected, my doctor told me to cut down on sodium. But he also told me to increase my potassium intake. Why?

DEAR READER: Sodium and potassium are two minerals that form salts. Your question reminded me of a patient I look care of long ago, who also had a high blood pressure problem. I asked her to substitute potassium salt for the usual table salt (which contains sodium). I'll tell you what happened later. People with diets high in potassium have lower blood pressures than those with potassium-poor diets.

Is there a way to prevent delirium during a long hospital stay?

DEAR DOCTOR K: My elderly mother has a number of health conditions. Over the past year, she has ended up in the hospital four times. The last two times, she became delirious. Is there anything we can do to prevent delirium if she has to have another hospital stay?

DEAR READER: Unfortunately, delirium is common among older patients in hospitals, particularly after surgery or during a stay in an intensive care unit (ICU). One-third to two-thirds of elderly hospital patients develop delirium.

I haven’t had my usual energy recently, should I see my doctor?

DEAR DOCTOR K: For the past few months I just haven't had my usual energy. Should I see a doctor?

DEAR READER: We all have times when we lack energy; it's a universal human experience. We can often pinpoint the cause: hard physical or mental work, an ongoing stressful situation, lack of enough good-quality sleep. Most people probably also experience times when they lack energy or feel unusually tired but cannot pinpoint the cause.

Where is the line between perfectionism and OCD?

DEAR DOCTOR K: I think of myself as a perfectionist. But more than one person has jokingly referred to me as "OCD." Where is the line between the two?

DEAR READER: Where is the line between a common way of behaving and a mental health disorder? It's a common question, and I'm not sure it can ever have a definite answer on which everyone would agree. First of all, when is perfectionism a good thing, and when is it a human tendency that goes overboard? My answer: Perfectionism is a good thing if the goal at hand absolutely requires it.

I’m losing patches of hair, is this normal or do I have alopecia?

DEAR DOCTOR K: I'm a man in my 40s, and I've suddenly started to lose patches of hair, but only on certain parts of my head. What's going on?

DEAR READER: What you are describing does not sound like normal baldness, which typically affects a certain part of the head, not patches of hair loss here and there. Instead, it sounds like you could have a condition called alopecia areata. This skin disorder causes hair loss, usually in small round or oval patches, most often on the scalp. The bald patches tend to appear suddenly and affect only a limited area.

What could cause irregular bleeding all month long?

DEAR DOCTOR K: My periods used to be pretty regular. But for the past few months, I've been spotting all month long. Why is this happening?

DEAR READER: There are many possible explanations. Fortunately, few of them can turn into serious problems. Before talking about the causes of abnormal bleeding from the uterus, it's worth reviewing the menstrual cycle. Normally, the cycle is triggered by signals from sex hormones. Hormones made in the brain travel to the ovaries, leading to the production of other hormones by the ovaries: estrogen and progesterone.

Aren’t antibiotics supposed to kill bacteria? If so, how did I get C. diff?

DEAR DOCTOR K: I took an antibiotic before having some dental work done. I ended up in the hospital with severe diarrhea caused by something called "C. diff." I was told it was a kind of bacteria, but aren't antibiotics supposed to kill bacteria? Can you explain?

DEAR READER: You heard the doctors correctly: "C. diff" is shorthand for a bacterium known as Clostridium difficile. It lives inside our intestines, along with trillions of other bacteria. Normally, the harmful C. diff bacteria are far outnumbered by other bacteria in our intestines. These other bacteria keep C. diff under control. For this reason, we'll call them "good" bacteria.

If I exercise less than the recommended 150 minutes/week, will it still benefit my health?

DEAR DOCTOR K: You often recommend exercising for 30 minutes a day, most days of the week. That target intimidates me. Is it worth it for me to exercise less, say 15 minutes, three days a week? Or is there no benefit unless I commit to the full 150 minutes per week?

DEAR READER: I'm glad you asked that question, because there are a lot of people who are daunted by the thought of exercising that much -- and therefore don't do it at all. It is true that I do advise 150 minutes of moderate-intensity activity each week. But two recent studies, while not changing my view that 150 minutes is best, show that less than this still brings benefits.

Does long term use of antihistamines cause dementia?

DEAR DOCTOR K: I've been taking over-the-counter antihistamines for years to control my allergies. Now I hear I may have to worry about dementia. How real is the concern?

DEAR READER: Antihistamine drugs have "anticholinergic" (an-tee-cole-in-ER-jik) effects. That means that they have some tendency to block the action of a natural substance called acetylcholine. This substance transmits messages in the nervous system. In the brain, it is involved in learning and memory; in the rest of the body, it stimulates muscles to contract.