Dear Doctor: I am bothered by certain scents, especially from candles. What causes it? And other than moving away from the source, is there anything I can do to combat this problem?

Dear Reader: When it comes to having an adverse reaction to the scents and fragrances that are routinely added to thousands of products, you are far from alone. About a decade ago, researchers found that more than 30% of the general American population considered scented products irritating. A similar 2016 study put that number at nearly 35%. Participants in both studies reported that even brief exposure to a fragranced product could result in a migraine headache; trigger an asthma attack or other respiratory difficulty; and cause dizziness, fatigue, problems concentrating, numbness, nausea and skin rash. Scented and perfumed items that caused these problems included the candles that you struggle with, as well as cleaning products, laundry soaps, personal care products, dryer sheets, trash can liners and, of course, perfumes, aftershaves and colognes.

Scented products -- even those advertised as being natural, “green” or organic -- emit a wide array of volatile compounds, including some considered to be hazardous pollutants. We notice their scent when airborne molecules enter the nose and activate the complex network of receptor sites and nerves that translate a chemical structure into a specific smell. People who have an adverse reaction to these added scents are said to have a chemical sensitivity. Some are bothered by one or two types of chemicals, while others struggle with multiple sensitivities.

Unfortunately, it’s virtually impossible to identify exactly which compounds are at fault. That’s because, unlike the ingredients of a product, fragrance is considered to be a trade secret. Manufacturers aren’t required to disclose the specific chemicals they use to scent their products.

Awareness of the problem is growing. Some states are proposing laws to require manufacturers to disclose all chemical ingredients on their packaging. A 2016 legal ruling allowed multiple chemical sensitivity to be categorized as a disability, which lets -- or requires -- employers enforce fragrance-free policies when an employee has a condition that substantially limits one or more life activities. So if you have a minor allergy to a fragrance that causes a runny nose, you are not entitled to an accommodation, but if the allergy interferes with your breathing, you are.

Meanwhile, for the general population -- and in answer to your final question -- avoidance is the only real solution. And again, when you walk away to avoid the effects of a scented candle, you’re not alone. Studies have found that one-fifth of people will exit a store to avoid the headache or stuffy nose that airborne fragrances can cause. Fully 15% of people report missing work due to sensitivity to added scents or fragrances. Some even avoid washing their hands in a public bathroom that offers only scented soap.

You can learn more about the issue from the Chemical Sensitivity Foundation at chemicalsensitivityfoundation.org.

(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 husband and I are pretty strict about screen time with our kids. I read about a new study that indicates that screen time actually changes a child’s brain. Is this true? How much screen time is OK?

Dear Reader: As parents ourselves, we share your struggle when it comes to limiting screen time. But considering how we adults often struggle to put down the phone or step away from the computer, it’s not surprising that our kids face the same challenges.

Screens are so instantly absorbing, it’s all too easy to hand a fussy baby or toddler a phone while juggling several other tasks. And with so much social interaction now shifted to the online world, tweens and teens can feel cut off from their peers without screen access. Add in the increasing amount of schoolwork now done on computers and online, and it can feel like a screen-centric life is all but inevitable.

A recent study supports a growing body of research that suggests it’s time to rethink our acceptance of screens. Published last November in the journal JAMA Pediatrics, it found a link between screen time and a drop in language and literacy skills among young children. Not only that, brain scans found that kids who spent a lot of time in front of a screen experienced certain changes to the physical structures of their brains.

The researchers began by assessing the cognitive abilities of 47 children between the ages of 3 and 5. They also gathered detailed information about screen habits from the children’s parents. MRI scans of the children’s brains revealed that those who exceeded the recommended one hour of screen time per day had lower levels of development and organization in brain tissues known as white matter. White matter is made up of long nerve fibers surrounded by fatty protective tissues, and it plays a key role in language development and cognitive skills.

The children with higher screen time and structural brain changes also had poorer outcomes on tests measuring language and literacy skills. This all sounds dire, so it’s important to note that this was a small study with a narrow scope. The authors noted that the question of screen time for children deserves further study.

As for how much screen time is OK, that’s the big question right now. According to updated guidelines from the American Academy of Pediatrics, children younger than 18 months should have no screen time at all, other than video chatting with parental supervision. For children between ages 2 and 5, the AAP recommends a maximum of one hour of high-quality programming per day, watched with a parent present to explain what they are seeing. After age 6, the advice is consistent limits that maximize physical and mental health, as well as face time with family and friends.

It’s important that as parents, we lead by example and step away from our own screens.

(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: Our grandfather won’t use his hearing aid because he doesn’t like how it makes things sound. However, I recently read that using a hearing aid reduces the risk of dementia. How can we get him to use one?

Dear Reader: Your grandfather isn’t alone in his reluctance to use a hearing aid. Many people with hearing loss wait as long as 10 years before finally agreeing to seek help. Meanwhile, poor hearing hinders their ability to communicate and interact with family, friends and the world at large. This leads to isolation and depression, and as a growing body of research shows, also increases the risk of cognitive decline.

A study published in the Journal of the American Geriatrics Society last fall found that when older adults with hearing loss used a hearing aid within three years of their diagnosis, they had measurably better outcomes in several important health categories than those who didn’t correct their hearing. Those who used a hearing aid had lower rates of dementia and depression, as well as fewer injuries due to falls.

The researchers examined eight years of insurance data for almost 115,000 women and men over age 66 who were diagnosed with hearing loss. They found that the risk of a dementia diagnosis, including Alzheimer’s disease, was 18% lower among the hearing aid users. The risk of becoming injured in a fall dropped 11%, and the risk of depression was also 11% lower. Their findings are consistent with previous research that established a clear connection between even mild uncorrected hearing loss and an increased risk of dementia and depression.

The next step in the research is to pinpoint how and why uncorrected hearing loss is tied to dementia and cognitive decline. One theory is that hearing loss leads to structural changes in the brain, which in turn affect memory. Another ties it to the profound social isolation that hearing loss can cause.

Meanwhile, your efforts to persuade your grandfather to use a hearing aid aren’t unusual. The insurance data used in the study revealed that, among those diagnosed with hearing loss, an average of only 12% went on to get hearing aids.

We think it’s encouraging that your grandfather already owns a device. He has shown himself to be open to improving his hearing and may just need a bit of help to get on the right track. Try talking to him about what, specifically, he doesn’t like about his current hearing aid. Then if you have the time, do some research about the current technology and offer to help find a replacement.

Shopping for a hearing aid can be confusing and, with hearing loss, daunting. There are several types, with different fits and placements. Be sure your grandfather is using a reputable audiologist who can help him to find the perfect device. It’s possible that with ongoing support, your grandfather may be willing to give hearing aids another try.

(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.)