Dear Doctor: I was having a panic attack and thought I might faint. My dad had me breathe into a paper bag, and it helped me calm down. I’ve only ever seen that on TV. Why did it work? Was it because I ended up doing deep breathing?

Dear Reader: It’s interesting how, when a TV character hyperventilates, someone just happens to have a brown paper lunch bag for them to breathe into. And while the rhythmic nature of that breathing may contribute to calming down the person, the actual theory behind the maneuver is rooted in biochemistry. To understand why, let’s start with the anxiety attack. Often referred to a panic attack, it’s the sudden onset of symptoms associated with fear, despite the absence of genuine peril. Among the many unpleasant and unsettling symptoms of a panic attack is the rapid and uncontrolled breathing known as hyperventilating. When this happens, it quickly causes the concentrations of oxygen and carbon dioxide in the blood to get out of balance.

Unlike in controlled breathing, which allows the respiratory system to take in oxygen and expel carbon dioxide in optimal amounts, hyperventilation causes a surplus of oxygen and a deficit of carbon dioxide, also known as C02. Since C02 is a metabolic byproduct -- sometimes it’s referred to as a waste product -- that may not seem like a bad thing. Too much C02 dissolved in the blood can cause symptoms that range from dizziness, drowsiness, headache, confusion and shortness of breath to heart arrhythmias, seizures and loss of consciousness. However, too little C02 is also a problem.

Our blood has an optimal pH, which is maintained by a specific ratio of dissolved oxygen and carbon dioxide. When you hyperventilate, that ratio is disturbed. Too much oxygen causes the pH of the blood to rise and become too alkaline. This is known as respiratory alkalosis. Symptoms can include anxiety, dizziness, dry mouth, tingling in the fingers and arms, chest pain or tremors. In fact, some research has suggested a link between panic disorders and poor regulation of blood pH.

All of which brings us back to the person now breathing into a paper bag. With every exhale, they are filling the bag with C02. With every inhale, they make that C02 available to their over-oxygenated blood. When you inhale your own exhaled air, it’s known as rebreathing. The theory is that, after a moment or two, rebreathing will begin to stabilize blood pH and perhaps ease your symptoms.

However, it’s important to note that rebreathing is unsafe for certain people, particularly those with heart or lung problems. Having too little oxygen in the blood, which is known as hypoxemia, can share symptoms with an anxiety attack. These include shortness of breath, dizziness and rapid breathing. If someone experiencing hypoxemia practices rebreathing with a paper bag, they’re not only making their immediate condition worse, they’re putting themselves in danger. The bottom line is, unless you know beyond a shadow of a doubt that you’re hyperventilating due to an anxiety attack, leave the paper bag maneuver to the TV writers.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Hello again, dear readers, and welcome to the late-summer edition of the letters column. Along with so many of you, we’re facing record-breaking heat, high humidity and a few natural disasters. All the more reason to seek refuge in our ongoing chat about health and medicine.

-- Many of you continue to have questions about the novel coronavirus.

“If a sneeze can spread the virus, can exhaling also spread the virus?” a reader asked. “So many times I see people with their mask under their nose and want to say something, but do not because I do not want to get into a fight.”

It’s important to remember that we’re still in the earliest stages of learning about the novel coronavirus. Emerging research suggests that, in addition to respiratory droplets from a cough or a sneeze, the virus may also be present in the microdroplets expelled during breathing and speech. What isn’t yet clear is whether or not these are a major source of infection. We will keep an eye on that research and update any new findings.

When it comes to wearing a mask, you’re correct on two points. First, the mask should indeed cover both the nose and the mouth. It should also have a snug fit around the perimeter. And we think you’re wise not to comment on how someone else wears his or her mask. Unfortunately, this practice, which we engage in to protect each other, has become a hot-button issue. Better to move at least 6 feet away from that individual and go about your day.

-- And speaking of transmission: “Why aren’t belching and expectorating mentioned as vehicles for spreading the coronavirus?” a reader asked. “If I can smell the belched air, surely it’s possible for the virus to be suspended in it.” The act of spitting or emitting a large and sustained belch can send respiratory droplets into the air. Although it’s possible that these can spread the virus, they are not known to be a major means of transmission.

-- A reader who recently survived COVID-19 wrote to ask about the likelihood of becoming infected again. “I contracted COVID-19 on July 1, became ill and tested negative on July 21,” he wrote. “My symptoms were coughing, muscle aches and fatigue. Pneumonia ensued for two weeks. I then tested positive for antibodies on July 23. How concerned should I be about contracting it again?”

Unfortunately, the answer isn’t clear yet. Researchers in Hong Kong recently identified what appears to be the first known case of reinfection 4 1/2 months after a patient’s initial illness. This reinfection, with a slightly different strain of the virus, occurred when the young man traveled to Spain. Genomic testing revealed differences in the two variants of the virus, which researchers say proves this is indeed a reinfection rather than prolonged viral shedding. The young man had no symptoms, and researchers believe existing antibodies helped his immune system fight off the second infection. Still, the wisest course is to continue practicing all precautions to protect yourself and those around you.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My eye doctor says I have something called “drusen” on top of my retina. I’ve read that this is connected to macular degeneration, and I’m worried. Can you please explain more about it?

Dear Reader: The term “drusen” is the plural of the German word “druse,” which means node. In a medical context, drusen refers to small deposits of debris within the retina. That’s the layer of tissue that lines the back of the eye and contains light-sensing cells known as photoreceptors. Drusen are found not on top of the retina, as you mention in your question, but in an area known as Bruch’s membrane. It’s a very thin layer of cells that separates the upper layers of the retina, including the photoreceptors, from an area known as the choroid. This is a network of blood vessels that deliver oxygen and nutrients to the macula, the functional center of the retina.

In order to diagnose the presence of drusen, your eye doctor performs a dilated eye exam. It involves the use of special eye drops that prevent the iris, which is the part of the eye that controls the size of the pupil, from contracting. With the iris wide open, the doctor can then use either a special instrument to see into the back of the eye or a special camera to photograph the interior structures. Drusen will appear as yellowish-white spots within the retina.

Drusen are described as either hard or soft. Hard drusen are small and round, have well-defined borders and are often spread out. They are common as people age. Soft drusen are larger, have indistinct borders and tend to cluster together. Although both types of drusen should be monitored, hard drusen don’t usually cause vision problems. Soft drusen, which can cause damage to the macula, are associated with dry age-related macular degeneration. That’s a condition in which the macula deteriorates and the center of the field of vision is compromised or even lost. Drusen can also be present on the optic nerve, which can result in a slight loss of peripheral vision. This is more common in children than adults.

There is no treatment available for drusen at this time. However, someone diagnosed with soft drusen may be asked to take a specialized combination of vitamins and minerals that have shown promise in slowing a certain type of age-related macular degeneration. Using data drawn from a large study known as AREDS 2 (Age-Related Eye Disease Study 2), researchers developed a nutritional supplement that has been shown to reduce one’s risk of developing advanced age-related macular degeneration by about 25%. The formulation includes vitamins C and E, copper, zinc and a pair of plant pigments called lutein and zeaxanthin, all in specific proportions.

Since you’re worried, it’s important to speak with your doctor and have all of your questions and concerns addressed. Be sure to ask if the drusen found in your eyes are hard or soft, as each type signals a different level of risk. And be vigilant about all follow-up visits to monitor your progress.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)