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Health Support Center Waseda Branch Nurse Kinoshita

When dry, the virus spreads widely

It's the season when the temperature drops and the air feels dry. Viral infections spread when the air is dry, and this is related to the humidity in the air.

If the humidity is maintained at an appropriate level, virus-containing droplets from coughs and sneezes will quickly fall to the ground along with the moisture in the air. However, when the air becomes dry and the humidity drops below 40%, the water in the virus-containing droplets evaporates and becomes lighter, increasing the spread of the virus. Therefore, it is said that keeping the humidity above 40% can be expected to be effective in preventing colds and influenza infections.

Also for inflammation of the nose, throat and trachea, rough skin and dry hair.

Also, when the humidity is low, the mucous membranes of the nose, throat, and trachea, as well as the hairs that grow on the mucous membranes, tend to dry out. Mucous membranes and cilia normally have the function of catching foreign substances such as viruses and bacteria that invade from the outside and expelling them from the body. However, when these substances become dry, they become less effective, resulting in inflammation of the nose, throat, and trachea, making you more susceptible to colds and influenza.

Furthermore, when the atmosphere is dry, the moisture in the skin evaporates, causing the barrier function that protects the skin to disappear, leading to rough skin, itchy skin, and dry hair.

Easy humidification measures

To solve these problems, let's first introduce an easy way to humidify your home.

• Place a glass of water on the table
• Dry wet towels and laundry inside the room
• Leave the bathroom door open after bathing
• Wear a mask when you sleep (masks with wet filters have a more humidifying effect)
• Spray curtains, etc. with mist spray or room mist.

Direct fluid intake is also effective in protecting mucous membranes such as the nose and throat. In the winter, you don't feel thirsty and your water intake decreases, so it's important to be conscious about drinking water.

Precautions when humidifying

If too much humidification causes condensation to form on windows and walls, mold may grow indoors. Mold can easily cause bad odors and allergies, so be sure to maintain a moderate level of humidity (up to 60%).

There are easy ways to humidify your home even if you don't have a humidifier, so why not try it to prevent infections and skin problems?

[References]
・ AIR Lab. JOURNAL
・Harper.GJ: Airborne micro-organisms: survival tests with four viruses
J. Hyg., Camb. (1961) 59, 479-486.
・ “Guidelines for a Healthy and Comfortable Living Environment” 17 fields and 37 guidelines (Tokyo Metropolitan Government Bureau of Health and Medical Care)