As wildfire smoke blankets large swaths of the eastern United States, many people are experiencing physical symptoms, like prickling, stinging eyes; a scratchy throat; a runny nose; and some coughing. For those without underlying conditions, this will largely be a passing source of irritation. “You’ll be miserable a little bit, but you’ll be able to brush it off,” said Dr. Panagis Galiatsatos, a pulmonary and critical care medicine physician at Johns Hopkins Medicine.

But for those who are most vulnerable, even brief exposures can have immediate ramifications, as exposure to toxins in the smoke can trigger inflammation and exacerbate existing health issues. This group includes children and adults with respiratory or cardiovascular conditions. “For vulnerable populations, the brevity of exposure may be enough to flare up underlying lung issues, or conditions overall,” Dr. Galiatsatos said. Babies, young children, older adults and pregnant women are also at higher risk of serious health effects.

Everyone may want to take precautions, but doing so is particularly critical if you are vulnerable. Here’s what health experts advise to minimize your risk:

Monitor air quality.

“Don’t let your eyes be the sole deciding factor” to determine the air quality, Dr. Galiatsatos said. Monitor the local Air Quality Index, which can be found at AirNow.gov.

If the air quality is poor, stay inside as much as you can, said Dr. Samantha Green, a family physician at Unity Health Toronto. If the air quality is moderate and you have underlying conditions, you may want to continue to take precautions and minimize your time outside. Air Quality Index values above 100 mean that the air is unhealthy, and values between 51 and 100 are considered moderate.

“These toxins — if you can avoid them, avoid them,” Dr. Galiatsatos said. “Staying at home, windows closed, that would be the most ideal situation.”

Take precautions if you need to go outside.

Don’t exercise or perform strenuous activity outdoors, said Laura Corlin, an assistant professor at Tufts University School of Medicine. If you need to go outside, wear a tightfitting mask, like an N95. When you return home, change your clothes, Dr. Galiatsatos said.

The Centers for Disease Control and Prevention notes that dust masks, surgical masks and bandannas are not sufficient to protect children from smoke, and that N95 masks are typically not fitted for kids and may not provide adequate coverage. (Another well-fitting mask, like a KF94, can help.) The agency also said that breathing through a wet cloth would most likely not protect children from smoke.

Make your indoor space as safe as possible.

Experts advised keeping your windows closed. An air purifier like a HEPA filter can help, especially if it is in the room you spend the most time in. Dr. Corlin recommended minimizing activities that could interfere with indoor air quality: Don’t burn candles or use a fireplace, and don’t fry or broil meat.

Limit time with large groups.

Our immune systems work less effectively after we’ve been exposed to high levels of fine particulate matter in the air, said Dr. Francesca Dominici, a professor of biostatistics, population and data science at the Harvard T.H. Chan School of Public Health. If you are immunocompromised, you may want to limit unmasked indoor time with large groups of people, since you may be less able to fight off a virus someone passes to you.

Monitor your health.

Exposure to toxic air pollutants can raise the risk of heart attacks. If you are experiencing chest pain or shortness of breath, seek emergency attention.

For people with underlying respiratory conditions, like asthma or chronic bronchitis, watch out for exacerbated symptoms, like difficulty breathing or more intense coughing, Dr. Dominici said. If you are experiencing heightened symptoms, contact your doctor, who might suggest increasing medication.

Watch babies and young children to make sure that they are not struggling to breathe or excessively coughing, Dr. Dominici said. Parents may want to contact their children’s doctor if a child has asthma to see if they should alter their medication.