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The benefits and dangers of sunlight exposure to skin

July 21, 2021
Sunshine makes us happy, but is it our friend or foe? Or maybe both? Find out how to protect your body and maintain homeostasis for better health during the hot summer months.

Summer is here and people are more inclined to spend time outdoors. With the longer days, it makes sense that our bodies will be exposed to more sunshine. That can be both good and bad. I’ve often been perplexed about what to do when it comes to protecting my skin when I’m at the beach or in my garden. My dermatologist says to stay covered up or wear sunscreen. My primary physician recommends getting outside into the sun because I’m low on vitamin D. What’s a girl to do? What do I tell my patients, especially farmers, mothers, or the aging population?

As dental hygienists, we’re in a prime position to help our patients understand changes in their skin, what to look for, and when to see a dermatologist. Here’s what you need to know, and what you can share with your patients.

Striking a balance

Ultraviolet radiation is broadly divided into three categories: infrared radiation (IR), visible light (VIS), and UV radiation. IR is heat radiation and not detected by the human eye. The wavelength that is visible to the human eye is VIS. UV radiation is subdivided into UVA, UVB, and UVC.

  • UVA can penetrate through the skin and is not filtered by window glass. It is estimated that approximately 50% of exposure to UVA actually occurs in the shade. UVA rays are beneficial since they increase the production of vitamin D, but they can still damage and prematurely age the skin.
  • UVB is more associated with erythema and sunburn. It can cause immunosuppression and photocarcinogenesis. UVB is affected by latitude, altitude, season, time of the day, cloudiness, and the ozone layer.
  • UVC has the highest potential for biological damage and contains the highest amount of energy. It is effectively filtered by the ozone layer and as such isn’t considered to be a factor in solar exposure of humans.1

Our bodies are constantly working to find balance to stay healthy. When homeostasis is lost, health is compromised, and disease can result. Even something like a sunburn will shift the body’s balance.

The role of vitamin D

Vitamin D is a fat-soluble vitamin that is naturally present in some foods and added to others. It is produced when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis.2 Stored in the liver, vitamin D is a key component in our immune system. When the immune system is triggered, it is vitamin D that supplies the fuel. In that immune response, vitamin D also provides a boost of antimicrobial responses and suppression of pro-inflammatory mediators such as tumor necrosis factor-α. This is critical as tumor necrosis factor-α is associated with numerous health conditions such as rheumatoid arthritis, Crohn’s disease, atherosclerosis, psoriasis, diabetes, and obesity.3

Vitamin D is also important in calcium homeostasis and bone metabolism. The majority of vitamin D arises in the skin when triggered by UV radiation. In a double-blind study, participants who were given vitamin D supplements before sun exposure were found to have anti-inflammatory mediators and, therefore, sustained a reduction in skin redness. In contrast, those participants with lower vitamin D serum levels had significant expression of pro-inflammatory genes.4

Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal bone mineralization and mitigate involuntary contraction of muscles.3 Balance between vitamin D, calcium, and phosphorus is essential for optimal functioning of many tissues, organs, and cells. When the skin is overexposed to the sun and vitamin D is increased in the body, it will pull calcium out of the tissues into the blood and circulate at high levels, placing the body out of balance. One way to help keep the body in balance is to take a calcium supplement before going out into the sun. With the calcium already in the bloodstream, there is less risk of calcium being pulled out of the tissues. Data from studies on the nutrient supply of burn victims show deficiency in both calcium and vitamin D caused by wasting of one and synthetic failure of the other.5 There are currently no answers regarding the requirements for burn injuries in either children or adults, but scientists are making progress in understanding the body’s adaptive responses to those mechanisms.

Lack of vitamin D has also been linked to cancer.

Types of protection

The main destroying factors for the skin are free radicals, which are oxygenated molecules. When the skin is exposed to the sun, free radicals are released, causing skin damage. Understanding both sides of this equation is important: getting enough sun for vitamin D and avoiding too much sun to prevent formation of free radicals.

There are two types of sunscreens: chemical and physical. A chemical sunscreen absorbs the UV rays, while a physical sunblock reflects the harmful rays away from the skin. Most chemical sunblocks have a narrow spectrum, and so have several chemicals for each active region. Most have UVB protection, but only a few offer protection from UVA. Physical sunblocks are either zinc oxide or titanium dioxide. Both provide broad-spectrum UVA and UVB protection.

New advances

Today, many cosmetic companies have added sunscreen to makeup and lotions. Remember, the skin is the largest organ, and products used on the skin are absorbed into the body. There are natural sunblocks that can help protect the skin, yet do not carry the same risk as those made from chemicals. Even plant oils can resist the sun (sesame oil 30%), while others (coconut, peanut, olive, and cottonseed oil) can block out about 20% of UV rays. That’s because plants such as the olive tree have built-in protection against oxidative damage from the sun. That protection, called squalene, is the skin’s most important protective lipid.1 And there are other helpful plants.

Allantoin is a nucleotide that occurs naturally in the body and absorbs the spectrum of UV radiation that damages the cell’s fragile DNA. Allantoin is an extract of the comfrey plant and is used for its healing, soothing, and anti-irritating properties. Using allantoin can help counteract that damage. There are even clinical studies that confirm that allantoin enhances skin repair.1

Aloe vera is well known for its use after a sunburn, but has been demonstrated in studies to have a prophylactic effect if used before, during, and after sun exposure. Aloe vera not only improved fibroblast cell structure, but it also accelerated the collagen production process, making it a wonderful moisturizer and healing agent for the skin.1

How much is too much?

Experts agree that a minimum of 15 minutes of sun exposure of 18% of the body surface from 10 a.m. to 3 p.m. is all someone needs to absorb the necessary vitamin D; however, this is only really doable during the months of April through October.6 For the rest of the year, people need vitamin D supplements to prevent an imbalance.

Summer days and vacations outdoors typically expose the body to too much sunshine. Other than using a sunscreen, wearing clothing that is made with materials using UV protection is a great way to minimize sun damage or chemical risks. Also take into consideration factors such as latitude/longitude and pigment type when it comes to exposure risks. Obviously, those living farther from the equator with a darker pigmented skin will need longer sun exposure to achieve the same vitamin D uptake than someone who is closer to the equator with a lighter skin tone.

The bottom line

There is still much to discover about the body’s response to burns. The bottom line is keeping homeostasis by adjusting variables when exposed to the sun, whether it’s protecting the skin through a sunscreen lotion or clothing or supplementing with vitamin D and calcium prior to sun exposure.

Enjoying the outdoors is what I live for; however, living without disease is what I strive for. This season, perhaps, consider supplementation (consuming calcium-rich foods and drinks) and/or using a more natural approach to sunblock (sunscreens made with olive oil or clothing made with UV materials) to help your body maintain and live your best life.


1. Korać RR, Khambholja KM. Potential of herbs in skin protection from ultraviolet radiation. Phamacogn Rev. 2011; 5(10):164-173. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3263051/

2. Vitamin D fact sheet for health professionals. National Institutes of Health. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/

3. Parameswaran N, Patial S. Tumor necrosis factor-α signaling in macrophages. Crit Rev Eukaryot Gene Expr. 2010;20(2):87-103. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3066460/

4. Scott JF, Das LM, Ahsanuddin S, et al. Oral vitamin D rapidly attenuates inflammation from sunburn: an interventional study. J Invest Dermatol. 2017;137(10):2078-2086. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5610950/

5. Klein GL. Burns: Where has all the calcium (and vitamin D) gone? Adv Nutr. 2011;2(6):457-462. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3226383/

6. Kopiczko A. Assessment of intake of calcium and vitamin D and sun exposure in the context of osteoporosis risk in a study conducted on perimenopausal women. Menopause Rev. 2014;13(2):79-83. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4520343/#:~:text=Vitamin%20D%20is%20essential%20to,and%20can%20lead%20to%20osteomalacia

Dabney Vaccaro, BS, RDH, HC, is an instructor at O’Hehir University and has worked as a clinical hygienist for 19 years. As a lifelong learner, Dabney is interested in all things organic and is currently taking classes to be a clinical herbalist. She hopes to be able to integrate her herbal knowledge with her dental hygiene profession. Outside of teaching, clinic, and studying, she works to make organic teas and self-care products through her side hustle, Wild Herbals, found at shopwildherbals.com.