Dear Doctor: I heard two teenagers in line at the drug store talking about the skin microbiome and how you shouldn’t use soap on your face because it wipes out the good bacteria. We hear a lot about the gut microbiome lately, but is the skin microbiome really even a thing?

Dear Reader: The word “microbiome” refers to any community of microorganisms that live together peaceably in a specific environment. To reflect the fact that they don’t cause illness, it’s said that they “colonize” an area rather than “infect” it.

In terms of the human microbiome, we’re talking about the vast array of microbes that live upon and within our bodies. These colonies are typically composed of bacteria, bacteriophages, fungi, protozoa and viruses. Depending on their location, they number into the millions, billions and, in the gut microbiome, trillions.

In addition to the gut, anatomical sites of distinct microbiomes in and on the human body include the nose, mouth, esophagus, lungs, genitals and even the hidden depths of the belly button. And, yes, the skin, which is often referred to as the largest organ in the body, is the site of a microbiome. Multiple ones, in fact. They differ depending on their specific locations, and are affected by the variety of environments they interact with, including oily, moist and dry.

For instance, the skin between your toes, which spends long stretches of time in the moist darkness created by socks, shoes and perspiration, hosts a different profile of microbes than does the skin on your scalp, behind your ears or on the backs of your hands.

The epidermis, which is the top layer of the skin, is a tough environment for microbes. It’s dry, acidic and low in nutrients, and great swaths of it are exposed to the elements. And, yet, millions of bacteria, viruses and fungi find a way to make it their home. Depending on their location, they survive on the available proteins, oils, salt or moisture. Research shows that, as with our gut, many of the microbe colonies on our skin play a role in fending off potential pathogens. They also play a role in wound healing, in maintaining skin’s overall health and in how we smell. All of which is good reason to take a look at our bathing and skin care routines.

Dermatologists have long suggested that harsh soaps, too much scrubbing and daily bathing with overly hot water can strip the epidermis not only of helpful oils, but also wreak havoc on beneficial microbe colonies. To protect your skin’s microbiome, think in terms of gentle, pH-balanced soaps, and gentler overall treatment. That means save the scrubbing with loofas and brushes and other rough materials for the truly grubby areas. Instead of a vigorous rubbing with a towel when you are finished bathing, gently dab and pat your skin dry. And, in case you were wondering, you definitely want to keep up the vigilant hand washing that helps keep us safer during the coronavirus pandemic.

(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: I was diagnosed with trigeminal neuralgia a few months ago, which I had never heard of before. I have learned that successful treatment can vary from patient to patient. Can you address this disease in your column?

Dear Reader: Trigeminal neuralgia is a rare and extremely painful condition that occurs when the proper functioning of the trigeminal nerve becomes disrupted. This is the fifth cranial nerve, which is actually a pair of nerves that originate in the brain and run to the left and right sides of the face. Each side of the nerve is made up of three distinct branches. They provide sensation to the upper, middle and lower portions of the face, and also to the oral cavity.

When someone has trigeminal neuralgia, or TN, they experience sudden and severe bolts of intense pain that last anywhere from a few seconds to a few minutes. They occur between the jaw and the forehead, usually on just one side of the face, and often arrive in clusters. People describe TN’s piercing pain as akin to an electric shock. The sensations can be triggered by the slightest touch or vibration, so actions like putting on makeup, shaving, brushing one’s teeth or even being exposed to a breath of wind can lead to excruciating pain. The intensity of the pain, as well as its unpredictability, can become debilitating. It isn’t known why, but trigeminal neuralgia rarely occurs during sleep.

Although TN can occur at any age, it has been linked to the aging process and is most often seen in people over the age of 50. It’s also more common in women than in men. The main cause is believed to be contact between the trigeminal nerve and one of the blood vessels located where the nerve exits the brainstem. There is some evidence that TN runs in families. Researchers suspect this may be due to inherited blood vessel configurations. The condition is also associated with disorders such as multiple sclerosis, in which the protective myelin sheath that covers many of the nerves in the body suffers damage.

Treatment for TN begins with medications. Anticonvulsants and antispasmodics have been found to be somewhat successful at suppressing the trigeminal nerve’s sporadic firing. Up to 90% of patients report at least partial pain relief. Unfortunately, the effectiveness of these drugs often plateaus and then fades. Some patients find they are unable to tolerate the drugs’ challenging side effects, which can include dizziness, nausea, fatigue, drowsiness and tremor.

When drug therapies prove ineffective, surgery can become an option. This ranges from the use of radiation or chemicals to damage the nerve and “jumble” the pain pathways, to major surgery to separate the trigeminal nerve from the blood vessel that is compressing it.

Most recently, several small studies have found localized injections of Botox to be quite effective at suppressing nerve activity. This resulted in markedly fewer episodes and less pain. Study participants reported that the benefits lasted for three or more months. Although this is a promising avenue of inquiry, Botox is not yet an approved treatment for TN.

(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: I had trouble opening my mouth wide when I was getting my teeth cleaned, and the hygienist said it could be TMJ. But my sister, who is a chiropractor, says she thinks it’s a muscle spasm. What is TMJ, anyway?

Dear Reader: TMJ refers to the temporomandibular joint, which connects the jaw to the skull. We each have two, one on each side of the jaw. These are the structures that allow us to open and close our jaw, move it from side to side and back to front. The temporomandibular joint, which is a sliding hinge joint, is a complex and delicate mechanism. It gets almost nonstop use as we speak, chew, yawn, smile and swallow. For some people, the joint continues to get a workout throughout the sleep cycle as they clench their jaws or grind their teeth.

When the joint stops working properly, it’s known as a temporomandibular disorder, or TMD. However, this type of malfunction has widely come to be referred to simply as TMJ.

Symptoms of a TMJ disorder can range from quite mild, such as an occasional clicking sound while chewing, to severe enough to interfere with eating or speaking. Someone having problems with this joint may experience tenderness or pain within the joint itself, in or around the ear, or in other areas of the face. The joint may make crackling or popping sounds when in motion, and it can lock, making it difficult, or even impossible, to fully open or close the mouth. Malfunction in the joint can cause tinnitus, which is a ringing sound in the ear, or other noise that isn’t caused by an outside stimulus.

Your sister’s suggestion that your range-of-motion problem is related to the muscles in the jaw refers to a condition known as trismus. It’s sometimes called lockjaw, which brings to mind the muscle contractions associated with tetanus. However, these days, trismus refers to any muscle spasm within the temporomandibular joint that limits range of motion. It occurs when the muscles we use in chewing contract and don’t release.

When someone can’t open his or her mouth wider than 1.3 inches, they are considered to have trismus. It can be caused by damage or injury to the jaw, and it can also arise as a result of TMD. Symptoms include the reduced range of motion you experienced, pain or cramping in the jaw that occurs with or without movement, and pain or difficulty when exerting pressure, as when eating.

Whether or not your jaw problem is due to TMD or trismus, we urge you to see your doctor or a TMD specialist for diagnosis. This will include a medical history, including information about recent dental procedures or physical injuries, an exam to rule out structural or other abnormalities, and measurements of how wide you can open your mouth. Depending on what is found, additional imaging studies may be requested. Treatment of TMD and trismus can include resting the jaw with a soft food diet, medications for pain, muscle relaxers, exercises to gently stretch the jaw, behavioral therapy and devices to prevent nighttime clenching. In rare cases, surgery may be required.

(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.)