The Effects of Humidity on the Human Body

The Effects of Humidity on the Human Body

As discussed in Home Humidity and Allergies, humidity directly affects the amount of allergens in the indoor environment. In particular, high humidity causes both dust mite populations and mold colonies to grow, thereby greatly increasing allergy sufferers’ total allergen load (shop our Allergy-Free Bedding to protect yourself from dust mites). While this touches on one side of the spectrum, your body can also feel the effects from the other side of the spectrum when there is low humidity. Starting with high humidity then continuing on to low humidity, we’ll explore the wide impact that humidity can have on each of us.

It may seem obvious, but even non-allergic individuals suffer from the effects of high humidity. No one enjoys sticky hot weather. But have you ever wondered why moist, hot air makes us feel so uncomfortable? Or, why extremely dry air can also cause discomfort (though for different reasons)? This article explains the effects that humidity has on the human body, and why keeping humidity levels within a specific range will keep your allergies under control and is important for your safety, too.

Effects of High Humidity on the Human Body

One reason humidity makes hot weather more unbearable is that the higher the relative humidity, the higher the temperature actually feels. For instance, a temperature of 95°F feels like 95°F when the relative humidity is 30%. But bump that humidity up to 65% and that same 95°F feels like a whopping 117°F! A heat index chart factors relative humidity into temperature to provide a more accurate assessment of what the temperature feels like. This is similar to what you see during the winter months regarding “wind chill”. In that instance, the speed of the wind is factored into the temperature to give a more accurate reading of how cold the weather actually feels to us.

But why does humidity make it feel hotter? To understand this, we have to understand how our bodies cool us down.

Humidity Hampers the Body’s Cool-Down Mechanism

Though we do not often think of it, we are inherently fragile creatures. Something as seemingly small as a five degree drop in body temperature can cause severe health consequences, including hypothermia. Five degrees higher and the human body begins to experience hyperthermia. So on either end of the spectrum, when the core body temperature begins to deviate from the norm, problems can occur.

When outside temperatures approach the temperature of the human body (about 98°F) the body undergoes a series of changes to help maintain a cool temperature. Sweating, altering the rate and depth of blood circulation, and increased respiration are all measures the body will take in an effort to cool itself down and shed excess heat.

Sweating, one of the key cooling mechanisms of the body, only works to cool us down if the water that is excreted through the skin is evaporated. This is where humidity comes in. The concentration of water in the air, relative to the temperature (relative humidity) determines the rate at which the water can evaporate from the skin. When the air is holding more moisture (relative to the total moisture it could hold at that temperature), it is harder for the air to absorb the sweat from our skin. The result? We continue to sweat, and instead of feeling any relief, we simply feel hot, sticky and uncomfortable. When high relative humidity continues to make you sweat and you are unable to cool down, your body has to find another way to cool off.

The Danger of High Humidity

High humidity makes us feel hotter and uncomfortable, but it also causes our core temperature to rise, causing our bodies to compensate by working harder and harder to cool us down. When sweating doesn’t work to cool us down and our bodies continue to heat up, it can result in overheating, which causes loss of the water, salt, and chemicals that the body needs. Overheating, or as it is more commonly known as, heat exhaustion, can lead to dehydration, chemical imbalances within the body, or in severe cases, death. As expressed on The Weather Doctor,

“And overheating can cause discomfort at the very least and death at the very worst. Continued loss of water and a variety of dissolved chemicals such as sodium chloride — salt — from the body, if not replenished, can cause dehydration and chemical imbalances. Dehydration depletes the body of water needed for sweating and thickens the blood, requiring more pressure to pump it through the body, thus straining the heart and blood vessels.”

Such effects are more pronounced and can be more dangerous depending on your age and overall physical condition. However, young people that aren’t aware that their physical activity or exercise could be dangerous in humid conditions, are also at risk. Overheating is a serious condition, and can result in the following (courtesy of USA Today):

• Heat cramps: Exercising in hot weather can lead to muscle cramps, especially in the legs, because of brief imbalances in body salts. Cramps become less frequent as a person becomes used to the heat.
• Heat syncope or fainting: Anyone not used to exercising in the heat can experience a quick drop in blood pressure that can lead to fainting. As with heat cramps, the cure is to take it easy.
• Heat exhaustion: Losing fluid and salt through perspiration or replacing them in an imbalanced way can lead to dizziness and weakness. Body temperature might rise, but not above 102°. In some cases victims, especially the elderly, should be hospitalized. Heat exhaustion is more likely after a few days of a heat wave than when one is just beginning. The best defense is to take it easy and drink plenty of water. Don’t take salt tablets without consulting a physician.
• Heatstroke: In some cases extreme heat can upset the body’s thermostat, causing body temperature to rise to 105° or higher. Symptoms are lethargy, confusion and unconsciousness. Even a suspicion that someone might be suffering from heatstroke requires immediate medical aid. Heatstroke can kill.

There are a number of ways to avoid overheating. First, you need to be aware of not only the temperature, but of the heat index, too. Be sure to drink plenty of water and to take it easy, slow down and cool off if you notice any signs of fatigue, headache or an increased pulse.

Keeping your indoor air at a comfortable and healthy humidity level is also very important—you can do this by running a dehumidifier in your home. While an air conditioner may remove some of the moisture from the air inside of your home, a dehumidifier is built specifically for that purpose. Often times a dehumidifier enables you to control both the humidity and the temperature inside of your home. The drier the air, the quicker you will cool down and the cooler your body will feel. In addition to creating a more comfortable living environment, a dehumidifier also works to reduce allergens that often thrive in warmer, more humid conditions.

Effects of Low Humidity on the Human Body

So far we have discussed how and why high humidity levels can impact the body, but what about extremely low humidity? Low humidity can also have a variety of effects on the human body. By understanding the inherent properties of water and keeping in mind that the body is composed of roughly 70% water, it’s not difficult to see how low humidity levels can also carry a set of adverse effects.

There are two ways that you can categorize water loss in the human body, “sensible” and “insensible”. No, this doesn’t refer to whether or not it makes sense to lose water. Instead, 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 a type of sensible water loss. Once it is gone, you can feel the difference, and as anyone who has ever taken a physical knows, it can also be measured. 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 insensible water loss. 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 your body.

There is a reason why it is recommended for individuals to consume eight glasses of water per day. The rates vary based on age, weight, and physical activity, but the adult body often loses well over 2 liters of water per day. While the majority of water loss is through urine, the number two and number three ways that your body loses water are via the skin and respiration—when relative humidity levels are extremely low, the rate of water loss from skin and respiration can increase. 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%. So, how does this impact the 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, the moisture is lost. The less humidity that is in the air you breathe, the more moisture your body will attempt to put back into it. There is also one other process at work during respiration that deals directly with the lungs. The body keeps the lungs moist, and as drier air enters the lungs, they naturally draw moisture out. As a result, the humidification that your lungs and respiratory passages perform makes the air breathable and contributes to the slow, but steady loss of moisture from the body.

In addition, your skin can have an effect your body’s moisture level. The skin is the largest organ in the human body, and as a semipermeable membrane, the skin can both lose or absorb moisture. Have you ever sat in the bathtub for quite a while only to find that your hands and feet are covered in wrinkly skin? While the exact mechanism hasn’t been pinned down, most scientists believe that this is because of the absorption of moisture by the outermost layer of your skin. When submerged in water, your skin is effectively bathed in 100% relative humidity. When the opposite is true and relative humidity levels are low, your skin can lose moisture at a more rapid pace than normal. A skin care routine that includes all-natural hypoallergenic skin care products such as the Vanicream product line can help to combat dry skin.

Symptoms of Low Humidity

The effects of low humidity are best expressed in two areas, the skin and respiratory system.

• Dry Nasal Passages: As more moisture is drawn from the mucus membranes to moisten dry air, the membranes can dry out quicker than the body can replenish the moisture. This can manifest itself as dry and even painfully cracked sinuses. It can even become so severe that it will cause the cracked sinuses to bleed. This is partly why many people experience nosebleeds during the drier, cooler fall and winter months.
• Sore or Scratchy Throat: The same process that draws moisture from your nasal passages can also have the same effect on your throat.
• More Illness: As the nasal passages dry out from low humidity, your body’s ability to trap and filter out the viruses and microbes that can cause illness decreases. When the sticky membranes lose their ability to filter, more microbes can pass through. Even worse, as the mucous membranes dry and crack, they provide a direct path to the bloodstream for pathogens. This is often the reason why the flu is so prevalent during the fall and winter months.

On the skin, low humidity can also leaves its mark:

• 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 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 the effects on your skin and airways, low humidity can even cause problems with your 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 the 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 how do you combat this? While spending time outdoors, there are a few things you can do, but dressing properly is the first step. Dressing appropriately and keeping your skin covered will help to slow moisture loss. The use of a cold weather mask can be particularly beneficial. Most masks trap some moisture and heat, but some are specifically designed to do so. Masks can help your nose and nasal passages in performing their primary respiration functions—warming the air, humidifying the air, and filtering the air (depending on which mask you select). By keeping some moisture and warmth trapped next to your face, you create a buffer zone between your airways and the colder, drier air.

No matter if you’re indoors or outdoors, staying hydrated is also extremely 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 help to soothe low-humidity symptoms. 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 forced-air heating systems can create.

As you can see, there can be a variety of negative health consequences to the body resulting from low or high humidity conditions. Maintaining a relative humidity level between 35% and 50% is often ideal since it not only allows the body to function normally, but it also prevents the growth of allergens like dust mites and mold. The key to remember is that relative humidity is dependent on the temperature. These two factors are integrally linked, and changes in one will affect the other. Keeping all of these things in mind can not only give you a better understanding of how your body functions in relation to your environment, but how to prevent some of the more negative health effects of humidity.