The negative effects of low humidity levels at home (and your work place)

During the winter season the humidity inside our houses/apartments is well below the recommended level of 40–50%. Extremely dry indoor air can cause quite some discomfort which can make the winter season even more unpleasant as most of us already consider it.

There are two types of ways that water loss is categorized in the human body, “sensible” and “insensible”. These terms refer to whether or not you actually perceive the loss of water (sense it) and if it can be directly measured. Urinating is “sensible” as you feel the difference once it is gone and it obviously can easily be measured too. Insensible water loss refers to the loss of water that isn’t often noticed by the individual and is much harder to measure. Water loss through the skin, via evaporation, is the primary example of this. Breathing is another example. Just as fogging your glasses or fogging up the windows in a car demonstrates, each time you exhale, water vapor leaves the body.

There’s a reason why it is recommended to consume approximately two laters of water each single day. While rates vary based on age, weight, and physical activity, the adult body often loses 2 liters of water per day (if not more!). While the majority of water loss is through urine, the number two and number three ways that water is lost is via the skin and respiration. When relative humidity levels are extremely low, the rate of water loss from skin and respiration can increase significantly. Particularly during the fall and winter months, relative humidity levels can drop dramatically. While in many areas it is not uncommon to see relative humidity above 80% during the summer, fall months can bring relative humidity levels as low as 20%.

How does this impact your body?

If you first consider respiration, note that the body actually humidifies the air you breathe. Starting in the nose but continuing throughout the respiratory tract, mucus membranes not only help to filter out debris and particles in the air, but they also moisten the air. When you exhale, this moisture is lost. The less humidity in the air you breathe, the more moisture your body attempts to put back into it. There is also one other process at work during respiration and that deals directly with the lungs. The body keeps the lungs moist, and as drier air enters it naturally draws moisture out. So, the combination of the humidifying that the lungs and the respiratory passages perform not only makes the air breathable but also contributes to the slow but steady loss of moisture from the body.

Then we have the skin. The skin is the largest organ in the human body, and as a semi-permeable membrane, the skin can both lose or absorb moisture. Have you ever sat in the bathtub for quite a while only to find your hands and feet covering in wrinkly skin? While the exact mechanism hasn’t been pinned down, most scientists believe this is because of the absorption of moisture by the outermost layer of skin. Submerged in water, the skin is effectively bathed in 100% relative humidity. When the opposite is true and relative humidity levels are low, the skin can lose moisture at a more rapid pace than normal.

Symptoms of low humidity

• Dry Nasal Passages: As more moisture is drawn from the mucus membranes to moisten dry air, the membranes can dry out quicker than the moisture can be replenished by the body. This can manifest itself as dry and even painfully cracked sinuses. It can become so severe that the cracked sinuses bleed. This is partly why many experience nosebleeds during the drier, cooler fall and winter months.
• Sore or Scratchy Throat: The same process that is drawing moisture from the nasal passages can also effect your throat.
• More Illness: As the nasal passages dry out from low humidity, the body’s ability to trap and filter out viruses and microbes that cause illness dips. When the sticky membranes lose their ability to filter, more microbes can pass through. Even worse, as the mucus membranes dry and crack, they provide a direct path to the bloodstream for pathogens. This is often why the flu is so prevalent during the fall and winter.
• Dry Skin: Itching is the most common symptom of this, and for those with eczema or sensitive skin, the problem can be more pronounced. Beyond simple itching, persistent dry skin can actually lead to tiny cracks and even bleeding. Like the cracking of sinuses, cracked skin again opens the body up to greater exposure to microbes and illness.
• Chapped Lips: This is likely the least harmful but most common symptom of low humidity.

Aside from effects on the skin and airways, low humidity can even cause problems with our eyes. As low humidity saps the body of moisture, it can increase the evaporation of tears. Visible tears are caused by the overproduction of moisture and subsequent inability of the canaliculi (portion of the tear duct located closest to the eye) to adequately drain away the tears. The result is an overflow, down our cheeks, but what we often don’t consider is that the eye is constantly bathed in moisture. Low humidity can disrupt the moisture balance and cause itching or even watery eyes.

So what can you do yourself?

Staying hydrated is therefore very important. While the use of lotions, moisturizers, and things like lip balm can help soothe symptoms of low humidity and slow moisture loss, replacing lost moisture remains the most effective way to restoring overall comfort. Indoors, the use of a home humidifier can be very helpful. These devices use a variety of methods to put moisture back into indoor air and restore comfort, lessening the effects of seasonal low humidity and the drying effect that heating systems can create.

Maintaining a relative humidity level between 40% and 50% in your house is recommended. You will typically feel better and are less likely to get sick. Additionally, when the humidity is higher in your house or apartment it will actually feel warmer too.