Dry air, characterized by low humidity, is common indoors, particularly during colder months when heating systems are active. Air is considered dry when relative humidity (RH) levels fall below 30%. This article explores how dry air affects the body, its connection to illness susceptibility, and practical ways to mitigate its effects.
How Dry Air Affects the Body
Dry air directly influences the body’s mucous membranes in the respiratory tract and eyes. When humidity levels are low, these membranes lose moisture, becoming dry and irritated. This can lead to discomfort, such as a scratchy throat or dry nasal passages, and may contribute to nosebleeds.
The skin also experiences effects from dry air. Low humidity draws moisture from its outermost layers, leading to dryness, flaking, or even cracking. This can result in itching and may worsen existing conditions like eczema. Reduced skin elasticity and a weakened barrier function can make the skin more vulnerable to irritants and allergens.
Dry air can irritate the eyes. It may affect the tear film, the protective layer that keeps the cornea moist, leading to increased evaporation of tears. Symptoms include burning sensations, itchiness, increased blinking, and a feeling of grittiness. Prolonged exposure can contribute to blurred vision and make the eyes more susceptible to irritation or infection.
Dry Air and Illness Susceptibility
Dry air compromises the body’s natural defenses against pathogens. The nose and throat serve as the first line of defense, filtering and humidifying inhaled air. Tiny, hair-like structures called cilia, covered by a layer of mucus, work to trap and remove airborne pollutants, including viruses and bacteria.
When air humidity is below 40% RH, this protective mucus layer can dry out, damaging the cilia and impairing their ability to clear contaminants. This reduced mucociliary clearance means viruses and bacteria are less effectively removed, increasing susceptibility to airborne infections. Low humidity can also hinder the immune response, preventing cilia from removing viral particles and reducing the ability of airway cells to repair damage.
Dry air also influences the survival and spread of viruses, such as those causing colds and flu. In low humidity, aerosol droplets containing viruses lose moisture, reducing in size and remaining airborne longer. This allows infectious microbes to disperse more easily and remain infectious for an extended duration. While dry air does not directly cause illness, it creates an environment where the body’s defenses are weakened, allowing pathogens to persist and spread more readily.
Mitigating the Effects of Dry Air
Addressing the effects of dry air involves adding moisture to the environment and directly to the body. Humidifiers are effective devices for increasing indoor humidity levels, with an ideal range between 40% and 60% relative humidity. Proper maintenance is important to prevent mold and bacteria growth. This includes:
Changing water daily.
Regularly cleaning the unit.
Using distilled water.
Replacing filters as recommended by the manufacturer.
Maintaining adequate hydration by drinking plenty of water is another way to counter the drying effects of low humidity. This helps keep internal tissues moist, supporting their normal function. Even during colder months, when thirst may be less apparent, consistent water intake remains important.
For direct relief of dry nasal passages, saline nasal sprays are beneficial. These non-medicated solutions, composed of salt and water, mimic the body’s natural fluids and help moisten and soothe irritated nasal tissues. Saline sprays also assist in flushing out allergens and irritants. Similarly, lubricating eye drops, also known as artificial tears, can alleviate dry and irritated eyes by replenishing moisture and supporting the natural tear film.