Hello again, dear readers, and welcome back to the monthly letters column. You’ve filled our mailboxes to the brim, so we’ll dive right in.

-- We recently discussed the series of shots required when someone is exposed to rabies. This prompted a letter from a reader in Virginia whose husband found a baby bat. ”He touched the bat with his foot (while wearing socks and shoes), and it flew off,” she wrote. “Then he got worried about rabies. Is there a test that can reassure someone they don’t have rabies?”

There is no single test for rabies in humans. Instead, several tests on samples of saliva, blood serum and spinal fluid are performed. The results show if infection has occurred. Rabies is nearly always transmitted through a bite. It is possible to get infected through surface contact with infected saliva, but it’s rare. In the scenario you describe, your husband did not come into direct contact with the bat.

-- In response to a column about gastroesophageal reflux disease, or GERD, a reader from Louisiana shared their approach to managing the condition. “A behavioral change that works for me to prevent GERD is the elimination of sugar from one’s diet,” they wrote. “Give it a try, and if it works, you have a solution. If not, no harm done.” The reader’s experience is backed by recent research. A study published last year in the American Journal of Gastroenterology found that people with GERD who reduced sugar improved the pH level in their esophagus and experienced fewer reflux episodes.

-- We’ve had several letters in reference to a column that included a discussion about hydration. One reader asked about distilled water. “I prefer the non-taste of distilled water, so that is what I normally drink,” she wrote. “But someone told me it’s bad for my body. Is that true?” It is safe to drink distilled water when accompanied by a balanced diet. That’s important because distilled water has been stripped of electrolytes and minerals, including calcium and magnesium. Although the primary source of minerals essential to human health is the foods we eat, water also plays a role. Some studies have found that relying solely on distilled water may contribute to lower levels of these important minerals.

This brings us to a letter from a reader from Nebraska who regularly drinks spring water and wonders if it contains minerals. The answer is yes. For people who dislike the taste of tap water, spring water can be a good alternative.

-- A column about balance that suggested standing on one foot as a useful strengthening exercise prompted a question from a reader. “Should I balance on one foot with bare feet or with shoes on?” they wrote. “I think there will be a significantly different result.” You’re correct that each scenario elicits a slightly different kinetic response. But since both involve the mechanics of balance, we think both would be useful.

Thank you, as always, for taking the time to write. We love hearing from you. We have had an unusual amount of mail recently and will add several bonus letter columns in the coming weeks.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: Our 7-year-old came home from school with an itchy eye. A few days later, all three of our kids, plus my husband and I, had pink eye. Our family doctor gave us antibiotic eyedrops, and it was gone in a few days. What causes pink eye? What can you do to keep it from spreading?

Dear Reader: Pink eye is the common name for an infection known as conjunctivitis. It’s the most frequent cause of eye inflammation and occurs in an area of the eye known as the conjunctiva. That’s a thin, clear membrane that covers the white of the eye and lines the inner eyelid. The conjunctiva protects the eye from potential irritants and pathogens. It is nourished by a dense network of minute blood vessels, and it is the site of numerous lymphatic vessels, which are involved in immune response. The conjunctiva also plays a role in producing tears and mucus, which keep the exposed surfaces of the eye moist and lubricated.

Viral infection accounts for about 80% of cases of conjunctivitis. The cause is usually an adenovirus. Bacterial conjunctivitis is seen more often in children than in adults. While not as common, fungi and parasites can also cause infectious conjunctivitis.

Once the infection is present, it can spread easily and quickly. If someone touches the contaminated fluid or discharge from an infected person’s eye and then touches their own eye, they can transfer the bacterium or virus. As with a cold or the flu, the microbes can also be spread via respiratory droplets.

Conjunctivitis can also be caused by noninfectious agents, such as irritants to the eye, as well as allergies. In those instances, the condition is not contagious.

Pink eye gets its name from its most prominent symptom. When someone develops this type of infection, that network of tiny blood vessels that we mentioned becomes inflamed. This causes the whites of the eye to turn pink, or even red. The inner eyelid often becomes swollen, the membranes of the eyes begin to itch or burn, and the eyes may begin to tear. When the cause of conjunctivitis is bacterial, a discharge is often present.

Treatment for all types of conjunctivitis begins with managing the symptoms. This includes using a warm compress every few hours to keep the eyelid and lashes clean and moist and artificial tears to ease itching and dryness. People who wear contact lenses should pause their use until the infection has cleared. When the source of the infection is bacterial, as occurred in your family, antibacterial eyedrops may be prescribed. But antibiotics don’t affect viruses. In viral cases of conjunctivitis, the infection must run its course. Conjunctivitis typically clears up in seven to 14 days.

Prevention hinges on hygiene. Wash hands before and after touching your eye. Change pillowcases daily while infection is active. Don’t share personal items, such as washcloths, medications, makeup or eyeglasses. Be sure to throw away eye drops, solutions or eye makeup that were used while the family was infected. If symptoms persist -- or if they are accompanied by pain, sensitivity to light or blurred vision -- it is important to see a doctor.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: What is the latest understanding, from a medical standpoint, about the safety of tattoos? I read about someone with a tattoo who received burns on his chest during an MRI. I also heard about tattoo ink interfering with X-ray results. Are these possible outcomes or simply urban legends?

Dear Reader: Tattoos, in which pigments are inserted into the top layer of skin to create a permanent mark or design, date back thousands of years. Historians cite tattooed mummified remains, which radiocarbon dating revealed to be at least 5,000 years old, as the earliest known examples of the practice. Over the millennia, tattoos have variously been used as charms, talismans, status symbols, decorations, declarations of beliefs and also as punishment. Today, with their sometimes-fraught history left behind, tattoos have become a widely accepted form of self-expression. Permanent makeup, which uses the tattoo process to reproduce the effects of cosmetics on lips, eyelids and eyebrows, is also growing in popularity.

Data collected in recent surveys suggest that from one-third to up to half of all adults in the United States have at least one tattoo. This has led to a growing awareness of the potential adverse effects of the practice.

Because the act of tattooing pierces the skin, bacterial or viral infection is a risk. This can occur if the inks are contaminated, if the tattoo artist’s tools or hands are not clean, or if the person fails to take proper care of their fresh tattoo while it is healing. Some people find they are allergic to pigments or other ingredients in the ink and develop an itchy rash with bumpy, scaly or flaky skin. And because the ink is permanent, the body’s response to it can persist, as well.

The tattoo process itself, during which the tattoo needle punctures the skin thousands of times per minute, can lead to the development of scar tissue, raised bumps known as granulomas or a thickening of the skin known as keloids. Medical data shows that about 5% of people who get a tattoo develop an infection, and up to 10% experience short-term complications.

You’re correct that tattoos have been known to interfere with certain types of medical scans, such as an MRI. When pigments in tattoo inks include metal ores, it is possible for them to interact with the magnetic field of the scanner. Surgeons doing biopsies have noted that nearby lymph nodes are sometimes stained with tattoo ink that has been absorbed and then carried off by immune cells. It’s possible that, if ferrous particles are present, the migrated ink can affect the appearance of a lymph node in an X-ray. However, these types of complications are quite rare. A hospital in Germany, where scans were performed on thousands of patients with tattoos, found that it occurs in less than 1% of cases.

But you bring up a good point: Tattoo inks are not regulated in the U.S., and manufacturers are not required to disclose their contents. In addition to researching the skill and safety of a specific tattoo artist, learning as much as possible about the inks that are used is a good idea.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)