Skin Care

Managing Your Exposure to Solar UV Radiation for Better Skin Health

With spring comes warmer weather and more opportunities to spend time outdoors exercising, recreating, gardening, etc. However, the intensity of solar radiation is also increasing, which means that precautions should be taken to reduce the likelihood of sunburns, and on the longer term, the risk of skin cancers and the photoaging of skin. Application of a sunscreen onto exposed skin surfaces is an important way of minimizing the potential for skin reddening. It should have a sun protection factor (SPF) value of 30 or higher and provide broad-spectrum protection against both ultraviolet A and B radiations. In addition, consider the use of a hat to cover your head and clothing to protect other exposed skin surfaces along with the use of sunglasses.

To enhance your skin care, though, there are additional considerations such as (1) the areas of your skin that you should focus on in reducing UV exposures and (2) whether you need to be concerned mainly about intermittent, high intensity UV exposures or long-term cumulative exposures to solar UV.

Exposure to Solar UV Radiation and the Risk of Skin Cancer

Epidemiological studies have shown that most skin cancers are concentrated on sun-exposed areas of the body, particularly the head and neck, followed by the body trunk (Narayanan et al. 2010). For example, Moan et al. (2015) reported that the relative tumor densities of squamous cell and basal cell carcinomas were much higher on the head than the body trunk for a Norwegian cohort. In contrast, they  found that the tumor densities for cutaneous melanoma were about the same on the head and torso.

These epidemiological findings suggest that the use of a hat while outdoors during periods of elevated solar UV would be an effective way of reducing UV exposures to the head and hence the risk of skin cancers. Wide-brimmed hats would provide additional protection to the neck area. Sunscreen applications to the face/neck are also beneficial for UV protection, however, Holman et al. (2015) showed that sunscreen use is fairly low for US adults--which limits its effectiveness in reducing skin cancers in the US population. Barriers to sunscreen use may be related to cost, knowledge of its benefits, inconvenience, forgetting, and a desire to tan (see Armstrong et al., 2009).

Another aspect of sun exposure that is very important to consider is that both intermittent and cumulative exposures are important risk factors in skin cancer formation! Squamous cell carcinomas are linked mainly to cumulative UV exposures, basal cell carcinomas are related to both intermittent and cumulative UV exposures, and cutaneous melanomas are primarily associated with intermittent (intense) exposures (Narayanan et al. 2010; Moan et al., 2015). 

Lifelong UV exposure-control practices should therefore be aimed at both intermittent and cumulative UV exposures in order to reduce the risks of skin cancer. Avoiding sunburns during adolescence and consciously limiting UV exposures via lifestyle choices such as wearing hats, protective clothing, applying sunscreen, etc. are all components of a healthy skin-care regimen.

Schedule Outdoor Activities to Times when the UV Index is Low

Sun-protection measures should be commensurate to the magnitude of UV solar radiation. And this means that you need to monitor UV radiation levels by time of day. For example, by limiting your time outdoors to the hours when UV radiation is low, you can dramatically cut down on exposures. Nevertheless, to ensure that UV levels are indeed low, it is imperative to monitor the expected UV Index (i.e., UVI), depicted in the next chart.

The UV Index for a given location can be simulated as a function of latitude, longitude, time of the year, surface elevation, and the level of ozone. Often the predicted values are referred to “blue sky” or “clear sky” results because the effects of cloud cover, airborne particulates, and reflected sunlight from snow, sand, etc. are not considered. Consequently, the predicted values are reasonable upper limits of the UVI for the given time and location.

The hourly UVI predicted for the location associated with the IP address of your computer or smartphone is shown in the chart below. Note the hours when the UVI is “Low” or “Moderate” in order to schedule activities outdoors for reduced exposures. If your planned outdoor activities will extend to the times when “High” to “Extreme” UVI levels are predicted to occur, then rely on sunscreen, hats, available shade, clothing, and sunglasses to control sun exposures.

Noontime UV Index Widget

Wrap Up

  • Given the elevated prevalence of skin cancers on the head and neck as well as the barriers to sunscreen use, consider wearing a hat (wide-brimmed preferred to baseball cap) as a lifestyle choice to reduce your skin cancer risk.
  • Epidemiological studies demonstrate that skin cancers are connected to both intermittent and cumulative, lifelong UV irradiation.
  • Parents should monitor their children's UV exposure to prevent sunburns, which are a risk factor for skin cancer later in life.
  • Monitoring the UV Index can help inform your daily activities and skin-care practices for avoiding UV stressors.


Armstrong, April W., Alice J. Watson, Maryanne Makredes, Jason E. Frangos, Alexandra B. Kimball, and Joseph C. Kvedar. 2009. “Text-Message Reminders to Improve Sunscreen Use: A Randomized, Controlled Trial Using Electronic Monitoring.” Archives of Dermatology 145: 1230–36.

Holman, Dawn M., Zahava Berkowitz, Gery P. Guy, Nikki A. Hawkins, Mona Saraiya, and Meg Watson. 2015. “Patterns of Sunscreen Use on the Face and Other Exposed Skin among US Adults.” Journal of the American Academy of Dermatology 73: 83–92.

Moan, Johan, Mantas Grigalavicius, Zivile Baturaite, Arne Dahlback, and Asta Juzeniene. 2015. “The Relationship between UV Exposure and Incidence of Skin Cancer.” Photodermatology, Photoimmunology & Photomedicine 31: 26–35.

Narayanan, Deevya L., Rao N. Saladi, and Joshua L. Fox. 2010. “Review: Ultraviolet Radiation and Skin Cancer.” International Journal of Dermatology 49: 978–86.



Monitor Indoor Air to Improve Your Dry Skin Care

Variations in the relative humidity and temperature of indoor air are directly linked to the temperature and water vapor content of outdoor air. Consequently, as the weather changes, the indoor drying stresses on skin also change—even though you can’t sense them. Adapting your skin care to the changing drying stresses requires two basic actions:

  • Monitoring the drying stresses on skin and
  • Managing the skin’s responses to those stressors.

As depicted in the accompanying diagram, a proactive approach to dry-skin prevention and care requires the monitoring of indoor humidity as well as the Dry Skin Index (DSI), which is a function of both relative humidity and temperature.

Proactive skin care to prevent and manage the potential for dry skin depends on the routine monitoring of indoor air for humidity and the Dry Skin Index. 

Proactive skin care to prevent and manage the potential for dry skin depends on the routine monitoring of indoor air for humidity and the Dry Skin Index. 

Each monitoring activity corresponds to a specific management action. In the case of humidity, it is the operation of a humidifier that releases water vapor to indoor air. For example, when relative humidity in a bedroom consistently drops below 40%, operating a room humidifier while you sleep will help reduce drying stresses and enhance skin hydration. Monitoring the DSI on a daily basis will inform your skin-care choices regarding the application of moisturizing lotions and creams to areas of your body that are prone to dryness or flaky skin.

The DSI Sense, which is now under development, is the only sensor device that will measure both indoor humidity and the Dry Skin Index to inform your skin care practices. Check out our product page for more information and then sign up to be notified about its status.

Track the Dry Skin Index for Better Skin Care during the Winter

If you experience dry, flaky skin—especially during the colder months of the year—then it will probably be beneficial for you to monitor changes in the Dry Skin Index (DSI). As I explain in another blog entry, this proprietary index measures the external drying stresses on skin caused by indoor humidity and temperature. Both of these parameters of indoor air change on a seasonal basis as a function of the levels of water vapor in outdoor air, building properties, severity of the heating season, etc.

Responding to Seasonal Changes in the Dry Skin Index

The chart below shows the monthly average DSI values calculated for a sample of houses in the northeastern US (based on data from Arena et al., 2010). The drying stresses on skin increase by almost a factor of 2 from the low value in July to the high in January. These seasonal changes in the DSI values directly coincide with the frequency of Internet searches for information regarding “dry skin” as well as “winter dry skin”. Unfortunately, because you really can’t sense the magnitude of these drying stresses on skin, it’s difficult to adapt skin-care practices in a timely manner to compensate for the external stressors. Consequently, skin-care practices are often “after-the-fact”, that is, you only consider the use of a moisturizing lotion or cream until after flaky, dry or itchy skin develops.

Average monthly values of the Dry Skin Index for a sample of houses in the northeastern US.

Average monthly values of the Dry Skin Index for a sample of houses in the northeastern US.

October marks the transition from the warm, humid summer months to the start of the heating season accompanied by cooler, drier outdoor air. If you are susceptible to dry skin during the fall and winter months, this is a good time to stock up on moisturizing lotions and creams when sales occur at your favorite skin-care shopping place.

Adjusting Dry Skin Care for Winter Cold Spells

The occurrence of “cold spells” during the winter will produce elevated drying stresses on skin. For example, the cold, dry air associated with an arctic air mass will drive indoor humidities lower, resulting in DSI levels that are higher than the monthly average values depicted in the chart above. If you’re not able to monitor the increased drying stresses on your skin that occur during such cold spells, you won’t be able to adjust your skin-care practices in a timely manner to maintain proper hydration of the stratum corneum—or the outer most layer of skin.

Buildings, Climate, and the Dry Skin Index

Residential populations living in buildings that do not easily retain moisture and/or have high air exchange rates with outdoor air will be exposed to elevated drying stresses on skin and thus have an increased risk of having cosmetic (i.e., flaky) dry skin conditions. The next chart depicts the DSI levels calculated for a sample of apartments in New York City (NYC) monitored by Quinn and Shaman (2017). Note that the levels are considerably higher than the values associated with the detached residences shown in the prior chart even though the residences are in essentially the same climatic zone! The average wintertime DSI for the detached residences is 6.6, compared with 8.1 for the NYC apartments.

Monthly average values of the Dry Skin Index for a sample of apartment buildings in New York City.

At such elevated drying stresses, the likelihood of flaky dry skin increases dramatically. In this situation, the use of a room humidifier becomes an important tool for reducing the DSI by increasing indoor humidity. Nevertheless, Quinn and Shaman (2017) found that ownership of a humidifier among the apartment residents was not associated with a significant increase in humidity. Perhaps if those residents had been able to monitor the drying stresses in their apartments, humidifier use would have increased to improve skin hydration.

Wrap Up

  • Millions of people live in cold climates where wintertime dry skin is a challenge to deal with.
  • Drying stresses on skin in indoor environments can vary considerably—even in the same climatic zone.
  • Monitoring drying stresses on skin can inform skin-care decisions ranging from the application of over-the-counter moisturizing lotions to the operation of humidifiers for nighttime hydration of skin.


Arena, Lois and Mantha, Pallavi and Karagiozis, Achilles N., Monitoring of Internal Moisture Loads in Residential Buildings (December 1, 2010). Available at SSRN:

Quinn, Ashlinn, and Jeffrey Shaman. 2017. “Indoor Temperature and Humidity in New York City Apartments during Winter.” Science of The Total Environment 583: 29–35.


Let October Be Your Skin Care Preparedness Month!

The month of October for most of the United States marks the transition between the warm, humid, part of the year and the cooler months that coincide with higher indoor drying stresses on skin due to lower indoor humidities and temperatures. As the map below shows, in early October, 2016, much of the western US had outdoor water vapor levels below 10 g/m3, while the levels in the Midwest and East were gradually trending toward that level.

Regional climatic conditions across the USA drive changes in outdoor water vapor levels, which in turn directly impact indoor humidities and associated drying stresses on skin.

Regional climatic conditions across the USA drive changes in outdoor water vapor levels, which in turn directly impact indoor humidities and associated drying stresses on skin.

During the next several months indoor drying stresses on skin will increase even more due to reduced humidities and temperatures as the heating season begins in earnest. So, in anticipation of those greater environmental stressors, it’s a good time to prepare for the associated skin-care requirements.  

Shop for Moisturizing Lotions and Creams

If your skin moisturizer needs replacement (time to check?), consider shopping for good deals now so that you avoid the higher costs of last minute shopping.  For your convenience, we have links to popular moisturizers at Amazon. Regardless of the moisturizer you select, remember that it’s the regular use of a moisturizer rather than its ingredients that is the real secret to dry skin care.

Check Out Room Humidifiers

If you have never used a room humidifier to deal with the low indoor humidities associated with the winter months, consider evaluating different brands that may suit your needs. One strategy is to use a humidifier in your bedroom while you sleep, which will help hydrate your skin as well as your nasal passages.

The Secret Behind the Effective Use of Skin Moisturizers

Does this situation sound familiar...

You observe some flaky dry skin on your face, arms or legs and so then you decide to buy a moisturizing lotion or cream. But unless you already know what product you are going to purchase, it’s somewhat daunting to select a moisturizer because of the multiple brands available as well as the wide variety of different formulations and ingredients. Moreover, there can be significant differences in prices. Which moisturizer will be most effective for you? Is it important to buy a specific type of face lotion? How do you evaluate the various claims on the products? Should you choose an organic body lotion or perhaps a natural face moisturizer? What's all the buzz with coconut oil for skin?

There are bewildering arrays of ingredients in moisturizing lotions and creams, but take courage; dry skin care doesn’t fully depend on your choice of moisturizer!

There are bewildering arrays of ingredients in moisturizing lotions and creams, but take courage; dry skin care doesn’t fully depend on your choice of moisturizer!

But what if there is another factor, other than the moisturizing formulation or brand, that is actually more important in alleviating dry skin caused by exposure to indoor drying stresses? Well, the answer may come as surprise, but a recent study by Shim et al. (2016) of 80 people found that is was the consistent use of a moisturizer over a period of 4 weeks rather than its formulation that was the key is restoring the barrier function of dry skin.

The study participants (20 to 70 years of age) were randomly assigned to one of 5 treatment groups, and they each applied a preselected moisturizer (one of six formulations) to their left shin and a different one to their right shin. Baseline observations included clinical evaluations of skin dryness and instrumental measurements of skin hydration and the transepidermal water loss rate. At the end of the study period, there were no statistically significant differences in either clinical or instrumental measures between the moisturizers! The only commonality was the regular daily use of the lotions by the study participants over the course of 4 weeks.

These results are not an outlier, as other studies have also demonstrated the value of regular use of moisturizers for restoring impaired barrier function of skin (e.g., Carville et al. 2014; Kucharekova et al. 2003). So, the “secret” for maintaining healthy skin depends largely on your personal care practices, not on your skill in selecting the “best” moisturizer!

Take homes

  • The regular use of a moisturizing lotion or cream is undoubtedly the most important factor in restoring the barrier function of the stratum corneum and thus controlling dry skin caused by external drying stressors.
  • If you’re in a rush to deal with dry skin, then simply purchase any popular moisturizer (lotion or cream) and then moisturize regularly.
  • You may ultimately prefer one particular moisturizing brand after personal use and evaluation, however, the consistent application of that product to impacted skin will largely determine how effectively it supports your dry skin care.


Carville, Keryln, Gavin Leslie, Rebecca Osseiran-Moisson, Nelly Newall, and Gill Lewin. “The Effectiveness of a Twice-Daily Skin-Moisturising Regimen for Reducing the Incidence of Skin Tears.” International Wound Journal 11, (2014): 446–53. doi:10.1111/iwj.12326.

Kucharekova, M., P. C. M. Van De Kerkhof, and P. G. M. Van Der Valk. “A Randomized Comparison of an Emollient Containing Skin-Related Lipids with a Petrolatum-Based Emollient as Adjunct in the Treatment of Chronic Hand Dermatitis.” Contact Dermatitis 48, (2003): 293–99. doi:10.1034/j.1600-0536.2003.00119.x.

Shim, J.H., J.H. Park, J.H. Lee, D.Y. Lee, J.H. Lee, and J.M. Yang. “Moisturizers Are Effective in the Treatment of Xerosis Irrespectively from Their Particular Formulation: Results from a Prospective, Randomized, Double-Blind Controlled Trial.” Journal of the European Academy of Dermatology and Venereology 30, no. 2 (2016): 276–81. doi:10.1111/jdv.13472.

Automate your bedroom humidifier using a WeMo smart plug

Automate your bedroom humidifier using a WeMo smart plug

A bedroom humidifier can provide nighttime skin hydration as well as provide relief from dry eyes and dehydrated nasal passages. When indoor relative humidity levels decline due to seasonal changes in outdoor water vapor levels,  it is time to consider a room humidifier to increase humidity.  One way of ensuring that the humidifier is used consistently is to connect it to a WeMo smart switch that is operated by a Smartphone app.

Know your moisturizer ingredients: Petrolatum reduces water loss from skin

Know your moisturizer ingredients:  Petrolatum reduces water loss from skin

Most moisturizing lotions and creams include occlusive substances that inhibit the loss of water from skin. By reducing such water losses, the hydration status of your skin improves. In this article we provide a brief synopsis of petrolatum, which is one of the most popular occulsive ingredients.