Dear Doctors: Ever since I was little, I have absolutely hated the sound of other people chewing. Whenever I try to explain this to someone, they think I’m overreacting or even making it up. Is this something you have come across before? Does anyone know why it happens?

Dear Reader: You are describing a condition known as misophonia. The term comes from the Greek word “misos,” which means dislike or hatred, and “phonia,” which derives from the Greek word for speech or sound. The condition is marked by a powerful aversion to certain commonplace sounds. These can include mouth sounds such as chewing, swallowing, yawning, burping, breathing or throat clearing, and repetitive sounds, such as finger tapping, typing or the clicking of a pen. Hearing the specific sound triggers feelings of anxiety, disgust, anger and, in some cases, even rage.

For people who don’t experience misophonia, these sounds don’t even register, let alone provoke a reaction. As a result, as you have repeatedly experienced, trying to explain the condition can be frustrating.

Although it may not be widely known, misophonia is actually somewhat common. It is estimated that between 10% and 20% of people experience it. It appears more often in women, with between 15% and 25% being affected. It is also more likely to occur in people living with autism spectrum disorders, obsessive-compulsive disorder and those affected by post-traumatic stress. Genetics are also believed to play a role. The condition can develop at any age, but often emerges in early adolescence. Some people have just a single sound that incites a response, while others can have multiple triggers.

The cause of misophonia is not yet understood. Recent research points to possible structural anomalies in an area of the brain known as the anterior insular cortex. This is a type of processing center, located deep in the brain, that receives sensory input from multiple areas of the body. Among its many and complex roles is contributing to emotional response and aiding in the integration of sound. Brain scans have shown that when people with misophonia are exposed to their trigger sounds, activity in the anterior insular cortex spikes, and is significantly higher than in people without the condition.

There is no cure for the condition at this time. Instead, the focus is on management. Many people find that adding music, a sound machine or background TV to group mealtimes can successfully mask the mouth sounds that act as triggers. When out in public, using ear plugs, ear buds or sound-canceling headphones can be helpful. Various forms of psychotherapy, such as cognitive behavioral, group and talk therapy, can help ease the emotional stresses of the condition. Some people derive benefit from the use of certain medications, including beta blockers. These blunt the fight-or-flight symptoms of anxiety, sweating, muscle tension and increased heartbeat that often accompany misophonia.

Because the effects of misophonia are so unusual, it is possible to have the condition and not realize it. If anyone finds that the symptoms or circumstances we have discussed relate to them, don’t hesitate to bring them up with your health care provider.

(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 11-year-old son is fascinated with those astronauts who are stuck on the space station. One of the things he asks about a lot is how being in space for that long affects the human body. Do you know what the latest research says about that?

Dear Reader: You are referring to two American astronauts who arrived at the International Space Station last June for what was planned to be an eight-day mission. When the experimental spacecraft they had piloted developed technical difficulties, however, NASA decided the pair should wait for the arrival of a replacement spacecraft to make the return trip. As of New Year’s Day, the two astronauts had logged more than 200 days in space. They are not scheduled to return to Earth until at least March.

As the astronauts await their ride home, they are undergoing significant physiological changes. That’s because our bodies have evolved to both overcome and to utilize the pull of gravity. The absence of that constant resistance affects every cell, tissue, structure and biological system. That’s why astronauts in space spend hours each day exercising.

Without the pull of gravity to work against, muscle mass decreases and muscles begin to atrophy. Within several weeks, astronauts lose up to 10% to 20% of their lean muscle mass. Weightlessness erases the physical cues that trigger bone remodeling. This is the process in which new bone continuously replaces old bone. As a result, bone mass in astronauts decreases by 1% to 2% every month they spend in space.

Fluids change their behavior in the microgravity of space, as well. This adversely affects the heart, circulation and blood pressure; leads to persistent nasal congestion; causes tissues of the face and upper body to become swollen; affects the inner ear and vision; and even results in increased flatulence and constipation.

The vacuum of space also interferes with the production of red blood cells, resulting in a condition dubbed “space anemia.” Astronauts are exposed to higher amounts of ionizing radiation, which can increase cancer risk. There is also emerging evidence that space travel affects the structure of the human brain.

The newest research has found that living in space even causes changes to human DNA. This was discovered in a fascinating study of identical twin brothers Scott and Mark Kelly. Both are astronauts who have spent time in space. From March 2015 to March 2016, while Mark remained on Earth, Scott lived on the International Space Station. Upon Scott’s return after a year spent living in zero gravity, genetic analysis found that almost 1,000 of his chromosomes and genes worked differently than those of his twin brother.

The good news is many of the adverse effects of space travel resolve upon return to Earth. Some, such as the effects of fluid shifts, take only a short time. Others, including loss of muscle mass, bone density and cognitive effects, can take many months and intense rehabilitation to overcome. Some can be permanent. That has made the development of space suits and space craft to mitigate these effects a priority within the global space community.

(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: I got sick with a stomach bug, and it was so bad that my girlfriend insisted on me going to our local urgent care. They said I had norovirus. It lasted for three days, and it was miserable. Where does norovirus come from, and how can you avoid getting it?

Dear Reader: Being sick with any kind of stomach bug is deeply unpleasant. That said, norovirus is a notoriously nasty one. The symptoms come on suddenly, are typically quite severe and can cause the person to become dehydrated and weakened. This is particularly true in vulnerable populations, such as young children, older adults and people already weakened by chronic illness, surgery or medical treatments. Norovirus is highly contagious, easily transmissible and very difficult to eradicate. That means outbreaks are often seen in communal settings such as schools, restaurants, cruise ships, hospitals and nursing homes.

Norovirus is shed in an infected person’s vomit and stool. There is also evidence that the virus can be transmitted through saliva. You can become infected if you ingest as few as 10 viral particles. This can occur through contact with food, beverages, infected eating or cooking utensils, any surfaces an infected person touched, and with the infected person themselves. Anyone who is sickened by norovirus who fails to thoroughly wash their hands after using the bathroom can easily and widely transmit the illness.

The most common symptoms of illness include nausea, stomach cramps and severe and repeated vomiting and diarrhea. It is possible, but less common, for norovirus to cause a low-grade fever, chills, headache and body aches. Symptoms can begin from 12 hours to two days after initial contact with the virus. The person is infectious from the moment that symptoms begin, and for at least several days after they end. There is no medication for the illness. Treatment consists of rest, supportive care and plenty of fluids to replenish those lost during active symptoms.

In the United States, more than 2,500 norovirus outbreaks are reported each year, sickening more than 20 million people a year and causing 100,000 hospitalizations. It leads to about 900 deaths, mostly in older adults. According to the most recent data available from the Centers for Disease Control and Prevention, the U.S. saw 91 confirmed norovirus outbreaks in the first week of December 2024 alone. That’s more than double the number during the same week in the previous three years.

When a norovirus outbreak occurs, it takes time and ongoing vigilance to eradicate it. That means repeatedly disinfecting all of the items and surfaces that may have been contaminated by an infected person’s touch, or the aerosols of their vomit. (Yes, kind of gross, but important to know.) Repeated and thorough handwashing by everyone sharing a space with someone who is sick is crucial to staying healthy. Use disposable gloves and paper towels to clean up after the infected person, and immediately bag them and place them in the trash. Because the virus can be present in aerosols like sneezes and coughs, consider wearing a mask. Anyone sick with norovirus should stay home to avoid spreading the virus and infecting others.

(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.)