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What Happens to Your Lungs in Cold Weather

Never allow your lungs to dry out.

Stepping outside in freezing weather can really take your breath away—and not in the poetic Winter Wonderland sense. Breathing in cold air can feel like a Mack truck has taken up residence in your airways. Here's what's going on, biologically, that makes that happen—and when to worry.

What Happens to Your Lungs

When you take a breath of cold air, your lungs humidify and heat the air as it enters your body. You shift from nose to mouth breathing. Cold air is dry, and breathing it in can cause your airways to tighten and become irritated. That's what causes the familiar burning sensation that makes it slightly painful to breathe. "The main reason you may experience some pain when you exercise in the cold is because lungs don't like the cold," says Jonathan Parsons, MD, of the Ohio State University Wexner Medical Center.  

Just being exposed to cold air increases the number of granulocytes and macrophages—two types of white blood cells that engulf and destroy foreign invaders—in your lungs. At the same time, the drying nature of cold air can slow down mucociliary function, the lung's self-cleaning system that clears out particles and gases via mucus, making it more difficult for pollutants to be cleared, researchers say

Why That Can be Bad

When the cold air causes your airways to narrow (called a bronchoconstriction), that can worsen respiratory conditions like asthma and chronic obstructive pulmonary disease (COPD), making it hard to breathe. If you have a common cold or bronchitis, cold air can aggravate it.

But cold air's tough on lungs even if you don't normally have breathing difficulties. When it's cold, there's almost no moisture in the air, says Parsons, so your throat and lungs can dry out quickly if you're not adequately hydrated — they can even crack and bleed. Researchers have found that even winter athletes have higher rates of asthma and chronic cough.

When to Worry

If you have asthma or COPD, it's a good idea to take steps to help shield your lungs from the cold (read on to see which).   

Experts advise seeing a doctor if you have a cough for more than two weeks, you're coughing up thick green or brown phlegm, or you're running a fever of more than 101 degrees. You could have a respiratory infection that needs further treatment. 

And if you have chronic shortness of breath, wheezing or tightness in your chest, see your healthcare provider ASAP.

RELATED: 30 Things You Shouldn't Do When the Weather Gets Colder

What You Can Do

Number one: When you're out in the cold, bundle up. "It now seems that grandma was right after all, getting a chill can predispose a person to respiratory infection, including pneumonia," said Norman H. Edelman, MD, a scientific advisor for the American Lung Association. "As she would have recommended, dress warmly, keep your feet dry and your head covered."

Two: Try to breathe through your nose more often. The cilia in your nasal passages will help warm the air, reducing the chances it'll irritate your lungs.

Parsons recommends wearing a mask or scarf over your mouth whenever temps drop below 32 degrees. That will help heat and humidify the air you breathe, easing the strain on your lungs and reducing the burn.

If you exercise out in the cold, Parsons also advises taking a hot shower immediately after your workout to moisten dehydrated mucous membranes. And to live your happiest and healthiest life, don't miss these 70 Things You Should Never Do For Your Health.

Michael Martin
Michael Martin is a New York City-based writer and editor. Read more about Michael