Hello again, dear readers, and welcome to late summer! Please indulge us as we remind you (yes, again) to wear sunscreen, use bug sprays, watch for ticks and stay hydrated. We hope the recent columns about the dangers of excessive heat and the warning signs and physical effects of dehydration were of use to you.

-- Speaking of summer, here's an interesting tip from a reader about keeping kids safe in the water. "When swimming and diving, children should be reminded that they have grown taller and weigh more than they did a year ago," she wrote. These physical changes can mean that the spot where they safely dove or jumped into a pool or pond last summer may no longer be deep enough for them this year, she said.

-- Regarding the idea that some senior citizens feel safer taking their daily walks in an enclosed shopping mall, a reader had a different view. "People are more likely to maintain an exercise program if they do their walking in neighborhoods and parks, where the environment is pleasant, and the scenery is nice," he wrote. "A shopping mall is anything but pleasant and nice. By walking in neighborhoods and parks (progressive cities even provide special walking trails), people can exercise their bodies and their aesthetic sense at the same time."

-- After reading the column about sushi lovers who wound up with intestinal tapeworms after eating raw salmon, a reader in Gastonia, North Carolina, wondered about the safety of the canned salmon that's a regular lunch staple. The good news is that canned salmon is fully cooked and thus is not a risk for tapeworm.

-- A reader from Fresno, California, who suffers from fibromyalgia wrote to ask whether we know of any clinical trials that she could take part in. The best resource for identifying a clinical trial, which is a rigorously controlled study to evaluate a new medical, surgical or behavioral intervention, is the website clinicaltrials.gov. It's a database that contains both privately and publicly funded clinical studies that are being conducted throughout the world. Fill in the simple form on the home page, press enter, and you'll get a list of relevant research.

-- We recently cited a study that evaluated changes to muscle mass in obese adults in their 60s who were dieting to lose weight. It's an important topic because maintaining lean muscle mass is tied to healthy aging. The results of the study were surprising and, it seems, counterintuitive, and we got quite a few letters. We're happy to repeat (and confirm) the results.

In this study, participants who dieted and did aerobic walking lost more muscle mass than did those who dieted and did no exercise. The group that dieted and lifted weights lost the least muscle mass. Specifically, muscle mass accounted for 20 percent of weight lost in the walking group, 16 percent in the dieting alone group, and 10 percent of weight lost by the weight lifters. Total fat loss was significantly greater among those who combined exercise with diet than in those who only dieted. Dieters who are concerned about maintaining muscle mass may consider adding resistance training to their exercise routine.

(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 am a 66-year-old female currently recovering from Rocky Mountain spotted fever. I was prescribed Vibramycin and Atarax. I stopped taking the Atarax after a few days because of the confusion that I was experiencing. I am wondering, though, if there are any lasting effects of this rare disease?

Dear Reader: The most important aspect of Rocky Mountain spotted fever (RMSF) is the need for early diagnosis and treatment. The bacterium that causes RMSF, Rickettsia rickettsii, is transferred to humans through a tick bite. The disease was first identified in the Rocky Mountains and can occur anywhere in North or Central America, but it's most commonly found in the southeastern United States. Each year, an estimated 2,000 to 4,000 cases are diagnosed in the U.S.

Ticks transmit the bacteria to humans during feeding, with symptoms occurring two to 12 days later. Early signs include nausea, fever, muscle aches, headache and abdominal pain, which in children can be very severe. The spotted rash associated with RMSF, which is the most characteristic sign of the disease, occurs because the bacteria directly injure the skin's blood vessels.

You were fortunate to have your disease caught early. Before the use of antibiotics, RMSF was a deadly disease -- with a death rate between 20 percent and 80 percent. Today, however, the death rate is extremely low; in 2007, it was 0.3 percent. Higher death rates and greater complications are more likely in people younger than 4 or older than 60. African-Americans, men and people who abuse alcohol also face a greater risk of death and chronic complications.

Those complications are related to the severity of the disease. The bacteria can lead to inflammation within the brain, causing confusion, memory problems, seizures, difficulty controlling body movements, balance problems and falls. The bacteria can also affect vision and hearing, potentially leading to the inability to see or hear. Because the disease can affect the nerves that go to the limbs and bladder, patients can lose sensation and strength in the legs and/or arms, as well as bladder control. When the disease is severe, skin ulcerations can develop, potentially requiring skin grafts. Lastly and rarely, the organism can lead to abnormal heart rhythms and fluid in the lungs.

So, yes, there are lasting effects to the disease, but the likelihood of those depends upon the severity of the disease at the outset. That's one of the reasons why it's important to treat the disease early. Your early use of Vibramycin (doxycycline) helped prevent many of these severe effects. (As for Atarax, that's for itching -- and shouldn't affect the course of the illness one way or the other.)

Because you appear to have none of the neurologic, skin, heart or lung problems seen with severe RMSF, you're unlikely to ever develop them. Thus, you should have no lasting effects of the disease -- and no need to worry.

Still, your case highlights the importance of seeking immediate medical attention upon the development of this rare -- but still dangerous -- disease.

(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: One of our teens, who is obsessed with science and medicine, says she read a story that there's something in toothpaste that causes colon cancer. Now she's refusing to brush her teeth. Is there any truth to what she's read? If so, should we all stop using toothpaste?

Dear Reader: Your teen is referring to triclosan, a highly effective antimicrobial and antifungal agent. This won't make her happy, but it's found in more than 2,000 consumer products, including cleansers, personal care and household goods, and some pet supplies. That means it's found in everything from toothpaste, clothing and makeup to kitchenware, furniture and toys.

In 2016, the FDA stopped manufacturers from offering for sale any over-the-counter antiseptic wash products like liquid, foam and gel hand soaps, bar soaps and body washes that contain triclosan. The ruling came as a result of studies that found the compound can alter hormone regulation in animals, could have a hand in the development of antibiotic-resistant germs and might be harmful to the immune system. So far, the FDA hasn't stepped in to prevent the use of triclosan in toothpaste, where it is claimed to help protect against gingivitis. And for products like clothes, cookware, furniture and toys, which don't make health claims, the regulation of triclosan is up to the Environmental Protection Agency.

The reason your teen is talking about triclosan right now is the publicity generated by the results of a recent study, which linked even short-term oral exposure to triclosan with adverse effects on the colon and its colonies of beneficial bacteria. Before we get to the details, it's important to note that these studies were done on mice, and that further research regarding the effects of triclosan on humans is needed. However, because the mouse genome is similar to our own, with many shared genes, research in mice offers insights into certain risk factors that can extend to the human population.

Regarding this new study, mice who were fed a diet laced with triclosan over the course of three weeks wound up with inflammation of their colons. They also had a gut microbiome that was measurably depleted, particularly of Bifidobacterium, a strain that has been shown to fight inflammation. Another group of mice who had triclosan introduced into their diets and were then induced to develop inflammatory bowel disease had symptoms that were more severe, and colon damage that was more extensive, than the non-triclosan mice. Although some triclosan mice developed colon cancer with tumors that were larger and more aggressive than those of the non-triclosan mice, the researchers reported that the differences between the two groups were too small to be statistically reliable.

Because colon cancer is associated with inflammation, interest in these new triclosan studies is quite keen. We fully expect to see more research into the subject. In the meantime, no, we definitely don't think you should stop brushing your teeth. But there are toothpastes without triclosan, and identifying them for the family seems like a great project for the young scientist in your household.

(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.)