Judy Foreman

Nationally Sindicated Fitness, Health, and Medicine Columnist

My daughter is 4 and still uses a pacifier. Is this harming her teeth – or her psyche?

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Sucking a thumb or a pacifier usually does not result in long-term harm to a young child’s teeth, or the “bite” that occurs when lower and upper teeth are pressed together, so long as she stops by the time the permanent teeth come in, usually around age 6..

“But sucking a pacifier may have already caused some effect on her bite, depending on the length of time she uses the pacifier and how intensely she sucks,” said pediatric dentist, Dr. Man Wai Ng, Dentist-in-Chief at Children’s Hospital in Boston. Intense sucking can cause narrowing of the palate and affect the growth of the jaws.

In general, pacifiers “are very useful to children,” said Dr. Barbara Howard, assistant professor of pediatrics at Johns Hopkins University. “It provides physiological stabilization. It’s been shown to make digestion better, to calm a child down and to help get more oxygen into the system.”

But pacifier use is also associated with more ear infections because it creates a vacuum in the ear, which can suck fluid out of the bloodstream into the middle ear. Because pacifiers often fall on the ground, they may also be full of bacteria and viruses. Kids who fall asleep with a pacifier are also more likely to wake up during the night. Even if they put the pacifier back in themselves, their sleep has still been disrupted, said Howard.

In some cases, parents who can’t get a child to stop using a pacifier “aren’t very good at setting limits in general,” said Howard. These parents “can’t tolerate children being in any distress. But part of childhood is to get immunized against increasing stress while you are under the protection of your loving caregivers,” Howard said. One tactic is to have a ceremony to bury the pacifier in the garden, then focus the child’s attention on getting a “grown-up” toy. Or just throw the pacifier away.

How do sunscreens work?

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Sun protection works in two basic ways. Sun blocks are inert substances, which contain metallic pigments such as titanium dioxide and zinc oxide that scatter the sun’s rays so they don’t penetrate the skin. Sun screens are substances that absorb the photons from sunlight and react with them chemically so that they cannot damage the DNA in skin cells. Many products now on the market contain both sun screens and sun blocks.

Although it used to be thought that only ultraviolet light (UVB) could cause skin cancer, scientists now know that both UVB and UVA can do so, said Dr. John Williams, a dermatologist at Brigham and Women’s Hospital.

That means you have to protect yourself against both, and that’s where things get complicated. The SPF (sun protection factor) number on the package label refers only to UVB protection. (An SPF of 30 absorbs 95 percent of the sun’s UVB rays; higher numbers confer a modest additional amount of protection – an SPF of 50 absorbs 98 percent of the rays.)

So, to make sure you’re protected against both UVB and UVA, you need to pay attention not just to the SPF number but to the ingredients in the whole product. Look for titanium dioxide and zinc oxide, the only two FDA-approved sun blocks that protect against the whole spectrum of UVA light. Alternatively, look for a substance called avobenzone (also known as Parsol 1789), which is a relatively new sun screen that also protects against the entire UVA spectrum.

Bottom line? Choose any product that protects against both UVA and UVB and that does not irritate your skin on a daily basis. Also, be sure to apply sun protection half an hour before going out in the sun to allow the product to be absorbed by the skin, said Dr. A. David Rahimi, the CEO of Forever Young, a dermatology practice in Los Angeles. Then re-apply every few hours, especially after sweating or swimming. People with fair skins should use products with an SPF of at least 30.

Are mosquito repellents like DEET safe? Are there any other options?

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Yes, and yes.

DEET (N,N-dimethyl-meta-toluamide) is one of the most effective insect repellents known, an important weapon in the fight against West Nile Virus and other diseases spread by mosquitoes and ticks.

Some people still fear DEET because of 14 potentially-DEET related seizures over 40 years. But both the federal Centers for Disease Control and Prevention and the American Academy of Pediatrics now say that DEET can be used safely by adults and children over two months old. The two groups base their recommendations on safety studies by the Environmental Protection Agency.

Doctors used to think that children should use DEET only at low (10 percent) concentrations. Now they say that, for both adults and kids, it is just as safe and more effective to use the 30 percent concentration of DEET, which protects for more than 5 hours, much longer than the lower concentration, said Dr. Michael Shannon, chief of emergency medicine at Children’s Hospital in Boston and chair of the Committee on Environmental Health at the academy of pediatrics.

DEET should be used sparingly on exposed skin (not on skin under clothing). It should not be spread near the eyes and mouth, on the hands of young children or on cuts or irritated skin. Skin should be washed after returning indoors.

In April, the CDC announced that two new repellent ingredients – picaridin and oil of lemon eucalyptus – are comparable to DEET at certain concentrations. But it’s less clear whether the two new ingredients are as effective as DEET against ticks, warned Shannon.

Picaridin has long been available in mosquito repellents elsewhere in the world. This year for the first time, it is available in the US as Cutter Advanced insect repellent, though it will not protect for as many hours as 30 percent DEET, said Emily Zielinski-Gutierrez [cq], a behavioral scientist at CDC.

Oil of lemon eucalyptus is a plant-based repellent that is available in a variety of formulations in the US. A 30 percent solution of oil of lemon eucalyptus is equivalent to a 10 to 15% concentration of DEET.

I was in the hospital for knee surgery and got a terrible rash on my back. The nurses said it was probably from chemicals used t

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It could be. These rashes happen “with enough frequency that we do see it. They’re often due to the high amounts of bleach and whitening agents in the detergent” used in hospital laundering, said Dr. John Williams [cq] a dermatologist at Brigham and Women’s Hospital.

Commercial laundries use much harsher chemicals than people use at home, he said, and these agents can cause contact dermatitis, a rash that in most cases is simply a reaction to an irritating substance but 20 percent of the time is a genuine allergic reaction, in which immune cells gear up to fight the offending substance.

“Nurses are extremely sensitive to this issue,” said Dr. Buddy [cq] Cohen [cq], interim chairman of dermatology at the Johns Hopkins Children’s Center. In severe cases, they can put special blankets or other products between the patient and the bedsheet to protect sensitive areas.

But hospitalized patients can also get rashes for other reasons, including reactions to medications. Some people are also allergic to latex (an allergy that can be serious) and other materials used in some hospital mattresses.

Often, though, rashes occur simply because people are lying flat in bed, and sweat glands become blocked, said Dr. Barbara Gilchrest [cq], chairman of dermatology at the Boston University School of Medicine. The solution is to stay as comfortably cool and dry as possible, change position in bed, and use baby powder or a product called Zeasorb that absorbs moisture.

Does meditation offer any health benefits?

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Yes. The ancient Eastern practice of quieting the mind through a variety of techniques from simply focusing on one’s breathing to silently repeating a word or “mantra” has been shown to have measurable, beneficial effects on the body.

In Western terms, the “relaxation response,” a term coined years ago by Dr. Herbert Benson, president of the Mind/Body Medical Institute and associate professor of medicine at Harvard Medical School, has been shown to lower blood pressure, heart rate and respiration; to reduce anxiety, anger, hostility and mild to moderate depression; to help alleviate insomnia, premenstrual syndrome, hot flashes and infertility; and to relieve some types of pain, most notably tension headaches.

Beyond that, it gets tricky. A new study published yesterday in the American Journal of Cardiology claims that meditation may actually prolong life, though the flaws in the study make any firm conclusion uncertain.

The study, conducted by Dr. Robert H. Schneider, director of the Institute for Natural Medicine and Prevention at the Maharishi University of Management in Fairfield, Iowa, pooled data on 202 mildly hypertensive people from two previous, randomized, controlled studies published in 1989 and 1995. Those studies, said Schneider, showed that Transcendental Meditation, a form of meditation in which a person is given a “mantra” by a teacher and trained to use the technique to quiet the mind, lowered blood pressure after three to four months if done for 20 minutes twice a day.

In 200l, Schneider’s team looked at death records from the National Center for Health Statistics for the participants in these earlier studies. On average, the follow up period was 7.6 years. The researchers found the participants were more likely to be alive if they had practiced TM in the original studies. But – and it is a huge “but” – the sample was small and researchers had no way of knowing whether the meditators kept meditating after the initial studies.

The study “had its limitations,” said Benson” but it’s in the direction that should be explored further.”

What can you do about smelly feet and armpits?

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Lots, including washing a lot and keeping these areas as dry and cool as possible.

As you may have noticed, sweat, which helps regulate body temperature, smells different in different parts of the body. That’s because the skin contains different kinds of glands. The more common are the eccrine glands, which pump out salty water (sweat).

Sweaty feet smell bad because of bacteria that feed off this sweat and dead skin, said Dr. Robert Stern, chief of dermatology at Beth Israel Deaconess Medical Center. Some strong odors, like garlic, are also pumped out in sweat, he said. The bad smell of athlete’s feet is due to a combination of fungus and bacteria.

The armpits and groin also contain apocrine glands, which pump out a number of substances, including mate-attracting pheromones.

To combat odor, you can, in addition to washing, use baby powder to sop up sweat, leaving less for bacteria to feed on. Anti-perspirants reduce sweat by blocking eccrine glands. Deodorants are really just perfumes, though some also contain anti-perspirants.

For really bad foot odor, some people swear by anti-microbial socks that contain silver-coated nylon, which may inhibit the growth of bacteria. Other people swear by insoles containing super-activated charcoal and baking soda.

For people who sweat profusely, a condition called hyperhydrosis, a liquid solution called Drysol (available by prescription) can help “shrivel up sweat glands,” said Dr. Samuel Ahn, chief of endovascular surgery at the UCLA David Geffen School of Medicine. Botox injections, which deadens the nerves that trigger sweating, also helps, especially in the armpits. (Feet are too big and too sensitive for the 60 to 100 injections it would require.)

As a last resort, there’s surgery to remove pieces of the sympathetic nerves that supply the hands, armpits or feet. It can help, but a major risk is that it may actually increase sweating on the trunk.

What makes hair go gray? Can you go gray suddenly if you’re sick or upset?

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In young people, hair gets its characteristic blond, brown or black color from varying amounts of a pigment called melanin, the same pigment that colors skin. But with normal aging, hair follicles produce less and less melanin, allowing the underlying white color of hair to become apparent. A head of hair looks gray when some hair has turned white and the rest is still pigmented.

Some auto-immune problems, in which antibodies mistakenly attack parts of the body, including melanin-producing cells in hair follicles, can also lead to gray hair. If a person has Hashimoto’s disease, for instance, in which antibodies attack the thyroid gland, he or she may also have other antibodies that attack melanin-producing cells in follicles, said Dr. Adrian Dobs, an endocrinologist at Johns Hopkins University.

Another auto-immune problem called alopecia areata, in which hair falls out, can also appear to make a person go gray rapidly, said Dr.Howard Baden [cq], a dermatologist at Massachusetts General Hospital. “In this disease, colored hairs fall out while white hairs may not be affected. If that happens, you would turn gray rapidly, not because of a change in pigment but because the darker hairs fell out,” he said. When hair grows back, it comes in white.

Although age is the greatest predictor of gray hair, some people do turn gray “prematurely,” and sometimes this tendency runs in families, said Dobs.

There are only two ways to deal with gray hair. Love it or dye it.

My husband has brown eyes. Mine are blue. Our son’s are green. How is eye color inherited?

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Scientists used to think that inheritance of eye color followed simple, Mendelian rules, which held that there was a gene for brown eyes that was dominant and one for blue eyes, which was recessive.

It turns out that things are a bit more complicated than that. “It’s not that there is a brown pigment and a blue pigment and a green pigment. There is just one pigment, melanin, and how much you have determines the color of your eyes,” said Dr. Bonnie Henderson, director of the comprehensive ophthalmology service at Massachusetts Eye and Ear Infirmary.

People who are albinos, for instance, have no melanin at all, and their eyes look pink because of blood vessels in the back of the eye.

People with blue eyes have very little melanin, while people with brown eyes have a lot. People with green eyes are somewhere in between.

So far, scientists have discovered six genes for eye color, and there are undoubtedly more, said Nicholas Katsanis, an assistant professor of ophthalmology at the Institute of Genetic Medicine at Johns Hopkins Medical Institutes. Each of these genes contributes in a different way to the “life cycle” of melanin -? the amount produced and recycled within eye cells.

“Imagine a hat with different colored marbles inside,” Katsanis said. “You put your hand in, get a bunch of colors. Eye color is like that. It’s a combination of colors that is quasi-random but is controlled by the six genes you inherit from your mother and the six you get from your father.”

Is there such a thing as a cancer-prone personality?

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The answer is an emphatic no, according to Swedish and Danish researchers who conducted a study that was recently published online by the journal CANCER.

The idea that some people might have an increased risk of cancer – perhaps those who are extroverted, emotionally contained, or who have aggressive, Type A personalities has been an insidious, blame-the-victim kind of notion for decades. And some studies have suggested a link between personality traits and cancer.

But the huge, new study of nearly 30,000 Swedish twins who were followed for 25 years appears to settle the issue once and for all. The researchers studied two personality traits in particular, extroversion (a high tolerance for intense social activity) and neuroticism (high anxiety and high emotional arousal), and concluded that there is no link between these traits and cancer. “For now, we can conclude that our results add to the evidence that personality does not contribute to the development of cancer,” they wrote.

Debunking the personality-cancer hypothesis is important, said Ann Webster, a psychologist at the Mind/Body Medical Institute in Boston.

“Thank heavens someone has finally discovered this,” she said. “I never believed that hypothesis.”

“I am more interested in looking at people’s optimism, resilience, coping styles and willingness to make lifestyle changes.”

The connection between cancer and personality has been debunked, but behavior is still important, said Dr. LaMar McGinnis, a senior medical consultant for the American Cancer Society in Atlanta. He noted that smoking, excessive drinking, lack of exercise and obesity all contribute to cancer.

How long do the fatigue and “brain fog” last after general anesthesia for surgery?

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It depends – on your age, the specific drugs used, how long the surgery took and how healthy you were to start with. These days, most general anesthesia drugs are fairly short-acting, which means you wake up quickly and the drugs are mostly out of your system within a few hours, said Dr. Carl Rosow, an anesthesiologist at Massachusetts General Hospital.

But tiny amounts can linger for up to seven days – enough so that you may not feel completely normal, especially if you also have a drink or two.

Moreover, if you are one of the unlucky 20 to 40 percent of patients who have nausea and vomiting after general anesthesia, that can add considerably to your recovery time because of dehydration and weakness from not eating, said Dr. John Ulatowski, director and chair of the department of anesthesia and critical care at Johns Hopkins Medical Institutions.

It’s actually quite difficult to sort out how much of the fatigue and “cognitive dysfunction,” or temporarily decreased intellectual function, that often follow surgery is due to general anesthesia and how much to the surgery itself. Some post-operative cognitive dysfunction can even occur with regional anesthesia, in which pain is blocked in one part of the body and the patient is sedated, but not rendered fully unconscious. That suggests, said Rosow, that part of post-surgical malaise may be due to the outpouring of stress hormones and inflammatory substances called cytokines.

People also vary widely in their response to general anesthesia drugs. For an older person having lengthy, major surgery, it may take six months to feel normal, though much of that would likely be due to healing from the surgery itself. A younger person having a short, minor operation may feel fine and be back at work the next day.