Humidity, or the amount of water vapor in the air, is an important health variable that is easy to overlook… yet very easy to remedy. Ideal humidity is generally described as between 40 percent and 60 percent, although some experts believe it should be closer to 35-45 percent.
When humidity is higher than this, as is common in the summer, it can contribute to the growth of mold, dust mites, and fungus, making it particularly dangerous for people with asthma and allergies. Low humidity is equally dangerous, however, and may even lead to serious complications to your health.
During the winter months, heaters and cold temperatures may lead to dry air with low humidity. This dry air can lead to dry skin, irritated sinuses and throat, and itchy eyes.
Over time, exposure to low humidity can dry out and inflame the mucous membrane lining your respiratory tract. When this natural barrier is no longer working properly, it increases your risk of colds, the flu, and other infections. Further, in low humidity certain viruses may be able to survive longer, further increasing your risk of contracting an infection.
The authors of the study suggested that the interaction between temperature and humidity influence "nasal cooling" as the air moves through your nasal cavity. This nasal cooling is detected by "sensors" inside your nose, which stimulate the sensation of airflow being either easy or obstructed, with cooler air resulting in feelings of less obstruction.
While high humidity can trigger nasal congestion, very dry air (i.e. low humidity) is also known to increase feelings of congestion because drying out your sinus membranes can irritate them further. So depending on your individual circumstances, if the air in your home is excessively dry, then increasing the humidity may help.
Reduced humidity combined with colder temperatures tends to wreak havoc on your skin as well. Many suffer with dry, scaly, itchy skin during winter months even if they don't have a diagnosable skin problem like eczema.
This is commonly referred to as "winter itch," caused when your skin is depleted of moisture. Aside from the itching, dry air will draw moisture out of your skin, making small cracks on your skin's surface far more likely.
While it's rare for infectious agents on your skin to cause a problem (it is typically only an issue when you transfer that to your nose or mouth), cracked skin will increase your risk of getting sick by providing an entryway for potentially dangerous pathogens through the cracked skin.
"The majority of adverse health effects caused by relative humidity would be minimized by maintaining indoor levels between 40 and 60%. This would require humidification during winter in areas with cold winter climates. Humidification should preferably use evaporative or steam humidifiers, as cool mist humidifiers can disseminate aerosols contaminated with allergens."
If the air in your home is excessively dry, you're likely experiencing dry skin or a dry, scratchy throat. You may also have noticed your houseplants drying out, wallpaper peeling at the edges, or static electricity, which is a direct result of dry air.
A word of caution, especially if you decide to use a humidifier: you must be VERY careful about making sure your humidity levels are not too high, as the high humidity will cause mold to grow, which could devastate your health.
Additionally, the moist, warm environment of a humidifier is a breeding ground for bacteria and fungi, which travel out of the unit via a "toxic mist" that you later breathe in.
Research has shown that breathing in dirty mist from humidifiers can lead to lung problems, including infection, and humidifier use is actually associated with an increased risk of developing asthma in children.5 As mentioned, too much moisture in your air also increases the development of mold, which is a toxin you don't want to be breathing in on a daily basis.
So if you choose to use a humidifier, do so sparingly, making sure humidity levels do not get too high. A hygrometer, which you can find at most hardware stores, can measure the amount of moisture in your home's air so you can adjust your humidifier use accordingly. Some humidifiers also have a hygrometer built in.
According to Dr. Robert Ivker, D.O., former President of the American Holistic Medical Association, the ideal level of relative humidity for sinus health is between 35-45 percent. This level is also generally recommended to avoid mold damage in your home.
As far as using a humidifier goes, you'll also need to make sure you clean it often, at least once every three days using hydrogen peroxide to remove any film or mineral deposits. The water in the reservoir should be changed daily, and be sure the area around it (tabletops, windows, carpeting, curtains, etc.) are kept dry. If you have a central air heating system, the best humidifier is one that is built directly over your furnace and tied into a humidistat and water source so the entire process is automated and your home is evenly humidified.
I want to point out that high humidity is just as dangerous, and perhaps more so, than low humidity because of mold. Along with obvious places such as shower stalls and damp basements, there can be many hidden sources of mold in your home. Particularly, if you've had plumbing problems or leaks in your roof, mold may grow and release spores from places such as behind drywall, under carpet or carpet padding, or in wood.
The vast majority of people suffering from chronic respiratory infections are not aware that their problem may be related to mold exposure. And unfortunately, their physicians are also unaware, making appropriate treatment impossible. In addition to minor or major respiratory problems, molds can also cause a multitude of other problems, including skin rashes, gastrointestinal problems, genitourinary problems, immunosuppression, and hemorrhage.
Often, the first sign of a mold problem is a "musty" odor. You are probably familiar with the smell of mildew—mildew is simply a variety of mold. You could also notice bowed or buckled floorboards, discolored carpet, a new water stain on your wall, or black or white specks—all signs you could be developing a mold problem. You can find more details, including what to do if mold is present in your home, here.
If low humidity is drying out your skin, use the tips above to increase humidity. Remember, this is important not only for your skin but for protecting the integrity of your mucous membranes to reduce your risk of infection. When it comes to dry, flakey skin, however, animal-based omega-3 fat, such as krill oil, can play a very important role. Besides drinking plenty of water, it may be one of the best ways to hydrate your skin from the inside out.
Omega-3 fats help to normalize your skin fats and prevent dehydration in your cells. This keeps your skin cells strong and full of moisture, which can help to decrease the appearance of fine lines. Omega-3 fats can also help calm irritated skin, giving you a clearer, smoother complexion courtesy of its anti-inflammatory activity. So, as a first step, if you struggle with dry skin, make sure you are taking enough omega-3 fats. In the colder dry winter months, you may need to increase your dose.
If your skin is dry now, a simple remedy is pure coconut oil, which acts as a wonderful all-natural "anti-aging" moisturizer when applied topically. When absorbed into your skin and connective tissues, coconut oil helps to reduce the appearance of fine lines and wrinkles by helping to keep your connective tissues strong and supple. It also helps exfoliate the outer layer of dead skin cells, making your skin smoother.
Hydrating your skin from both the inside and out can make low humidity a bit more bearable, making you more comfortable while you adjust the moisture levels accordingly inside your home.
4 Environ Health Perspect. 1986 March; 65: 351–361.