Dear Doctor: My 10-year-old grandchild gets a bath only three times a week, and sometimes it's only twice a week. Is this normal? I thought that children should be bathed every day.

Dear Reader: While it's true that the ritual of a child's nightly bath has fixed itself into the popular culture, the reality of what's best is actually somewhat different. Back in the days before indoor plumbing and central heating, bathing was generally performed weekly in the United States. It was a family affair often performed on Saturday night, so that everyone would be their sweet-smelling best for church on Sunday.

As technological advances gave each house a furnace in the basement and hot running water in the bathroom, taking a bath was no longer a laborious chore. Add in the revolution wrought by understanding how infections are transmitted, and the link between physical cleanliness and good health was formed.

However, the zero tolerance of the medical environment doesn't transfer to the home. According to guidelines developed by the American Academy of Dermatology, your grandchild is perfectly fine with those three or even two baths per week. The reasoning is twofold.

First, unless he or she is playing in mud, crawling through public sandboxes or helping out with messy tasks, the average kid just doesn't get dirty enough to require a bath every day. The other consideration is something known as the skin barrier. That's the protective film of cells and lipids that make up the outermost layer of your skin. Sometimes called the lipid barrier, it's meant to keep your skin hydrated by preventing water and electrolytes from evaporating.

In children, the skin barrier is not yet fully developed. Too much soap and scrubbing and they run the risk of irritation, even infection. In addition, the skin is home to certain microbes and bacteria that are an important part of our immune systems. Daily washing diminishes their numbers.

So how often should your child be bathing?

With babies, three times a week is plenty. What's important is being vigilant about keeping the face, neck and diaper areas clean and -- this is just as important -- dry. If bath time is something your baby enjoys and you'd like to do it more often, go with just warm water and no soap.

Children between the ages of 6 and 11 should bathe at least once or twice a week. If they want to bathe more often, that's fine. Are they smelly or visibly dirty? Then they need a bath. Once kids hit puberty, dermatologists say daily bathing is a good idea.

To get off on the right foot with personal hygiene habits, make the activities fun. This includes teeth brushing, hair brushing, hand-washing and bathing. Toys, story times, charts with stickers or stars -- all can turn a daily chore into an enjoyable moment.

And while daily bathing up until adolescence is optional, proper hand-washing is not. From the time they're old enough to understand, be sure to teach your kids to wash their hands before eating, after using the bathroom, after blowing their noses and, of course, when they're just plain dirty.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I have a lot of urinary tract infections. My doctor told me not to drink anything with caffeine, but surely there must be something else I can do. Are there foods I should eat? Not eat?

Dear Reader: First, let me say that you have my sympathies. Urinary tract infections, though they have no outward signs, can be quite painful. Such infections are common, especially in women, who have a short urethra compared to men, meaning bacteria don't have far to travel in order to cause a problem. The majority of bacteria that cause these infections reside in the colon. These bacteria can colonize the area at the exit of a woman's urethra and, from there, move up the urinary tract to cause infections in the upper urethra, bladder or even kidney. These infections usually require antibiotics.

In younger women, sexual intercourse is a substantial risk factor for urinary tract infections, or UTIs, as are spermicide use and having a new sexual partner. Genetics likely play a role as well; daughters born to mothers with a history of UTIs have a greater likelihood of such infections. Further, those who have a UTI before age 15 have a greater chance of recurrent infections later in life.

After menopause, problems with bladder emptying, incontinence and bladder position increase the risk of UTIs. For post-menopausal women, vaginal estrogen can reduce infections, because it improves the natural bacterial flora in the vaginal area and decreases colonization of harmful bacteria. If you develop UTIs after sexual activity, urinating and increasing fluid intake after intercourse may decrease your chances of infection because these actions help flush the bacteria from the urethra.

If these measures -- not proven by any study -- don't reduce intercourse-related UTIs, a dose of antibiotics after intercourse might be warranted. But take care: With increased exposure comes a greater likelihood of bacterial resistance to that antibiotic.

Another alternative is the use of the probiotic Lactobacillus, which helps protect the vaginal area from the bacteria associated with urinary tract infections. It's not as effective as prophylactic antibiotics, but it can decrease infection frequency.

Cranberry extracts have shown an ability in the laboratory to stop bacteria from attaching to urinary tract cells, but studies of cranberry juice and tablets have been mixed. A combined study in 2012 did show a reduced risk of UTIs among women taking cranberry products, but many studies within the larger study showed no benefit.

Studies on caffeine intake and UTIs have been limited. Although caffeine does cause bladder irritability and may worsen the symptoms of urinary frequency and urgency that are seen with a UTI, the polyphenols in tea and coffee may create antibacterial activity within the urine.

A 2003 Finnish study showed that women who had a higher intake of yogurt containing probiotics and berry juice, like cranberry juice, had a lower rate of urinary tract infections. But the data have not been replicated, and the study did not adjust for confounding factors.

Overall, although some people advise women to avoid alcohol, sodas, spicy foods or citrus, I'm afraid there is no good research on specific diets to help stop recurrent UTIs. The best that science can support is cranberry extract tablets; probiotics or yogurt with Lactobacillus; some of the behavioral changes mentioned above; and doses of antibiotics.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: First, there was a "superbug bacteria"; now there's a "superbug fungus"? What is this new fungus that I've been reading about? More to the point, how worried should I be?

Dear Reader: Unfortunately, yes, a type of yeast known as Candida auris has been identified as a source of serious illness in a growing number of hospital patients, both in the United States and abroad. Not only is it resistant to existing treatments, it has also eluded efforts by health care personnel to halt its spread.

Yeasts are single-celled microorganisms that are members of the fungus kingdom, which also includes molds and mushrooms. They're everywhere -- in the soil, on vegetation, in waterways and on living creatures, including humans.

Candida yeasts are typically found in the intestinal tract, as well as on mucous membranes and other areas of warm, moist skin. While more than 150 species of Candida have been identified, only about 15 of them are known to cause infections.

For the most part, these tiny organisms live peaceably with their hosts, held in check by the other microbiota that call us humans home. However, factors like stress, taking antibiotics or antifungals, and a weak immune system, to name just a few, can lead to an overgrowth of Candida yeasts. This can result in symptoms such as itching, rash, fatigue or gastrointestinal distress, which vary depending on the area that is infected.

The good news is that most Candida infections are easy to recognize and respond well to treatment. If you've ever had athlete's foot, a vaginal yeast infection, jock itch, diaper rash or oral thrush, then you've had a Candida fungus skin infection. Nail fungus, also caused by Candida, is more difficult to eradicate due to its positioning beneath the nail bed.

The very bad news is that unlike its relatives, Candida auris is emerging as a serious health threat. First identified in 2009 in Japan, the organism has spread globally. As of August 2017, it was responsible for 112 infections in the U.S., more than half of those in 15 different New York City hospitals.

Candida auris is resistant to all three major classes of antifungal drugs. It persists in hospitals and is spread between patients. It's particularly dangerous to people with weak immune systems, such as newborns and the elderly. It can enter a patient's blood stream via wounds, as well as lines or tubes entering the body. Once in the body, it can cause serious invasive infections. Rapid response is crucial, but it is made difficult because Candida auris is difficult to identify.

At first, travel was suspected in the global spread of Candida auris. However, genome sequencing, which is basically a DNA fingerprint, revealed enough differences between regional strains to suggest the yeast has sprung up independently. Needless to say, all aspects of Candida auris are now under intense study.

For all these dire details, you don't have to be alarmed. In most cases, infections occurred in patients who were hospitalized, most of them for several weeks. In the meantime, identifying new treatments and stopping the spread of Candida auris has become an international priority.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)