Natural Sunscreen: How Does It Work?

To many, warmer weather means more time spent outside enjoying time with family and friends! Sun safety can help make these experiences that much more pleasant. Wearing sunscreen and practicing other sun-protective habits can significantly reduce the likelihood of sunburn, skin aging, and UV-induced skin cancers. (21) But what is natural sunscreen, and how does it protect the skin? Keep reading to learn about sunscreen ingredients, sun exposure as it relates to skin color, and how natural sunscreen works compared to chemical sunscreen.

How does the sun affect skin?

The sun emits electromagnetic energy as ultraviolet radiation (UVR) at different wavelengths, including ultraviolet A (UVA) and ultraviolet B (UVB) radiation. These different wavelengths exert various effects on human skin that are dependent on skin absorption patterns and melanin levels, a natural skin pigment. (7) The ozone layer, which acts as a shield in the earth’s stratosphere, absorbs 90% of UVB radiation and small amounts of UVA radiation. (7)

UVB vs. UVA radiation

Both UVB and UVA radiation are associated with damage to skin cells and DNA, and both can contribute to the development of skin cancers. (6) Sunburn is predominantly caused by UVB radiation, and UVA radiation is associated with skin aging and an increase in pigmentation (tanning). (7)

Although UVA rays emit less energy and don’t burn the skin, they can penetrate deeper into the skin, suppress the immune system, and indirectly damage DNA. (7) UVA radiation is divided into two types based on their spectrum of radiation: UVA1 and UVA2. Broad-spectrum sunscreens should absorb or deflect UVA1, UVA2, and UVB radiation. (7)

Skin color types

The amount of melanin found naturally in your skin can affect your susceptibility to sunburn and UV-induced skin cancers. For example, individuals with darker skin tones have higher levels of protective melanin in their skin in contrast to those with lighter skin tones. (6) Although the risk of sunburn and skin cancer may be lower for individuals with darker skin tones, proper sun protection is important for everyone. (22)

Did you know? People of color may develop certain types of skin cancer in areas infrequently exposed to the sun (e.g. legs, feet, inner mouth), often present with a serious and advanced stage of the disease, and compared to individuals with white skin tones, have a poorer prognosis and higher mortality rates. (1)(2)(3)(4)(11)

While there are limitations to categorizing skin color by a strict set of six types, the Fitzpatrick Skin Phototypes tool may be helpful in understanding how to incorporate information from this article into your sunscreen routine:

• Type 1. White skin that is pale, burns easily, and does not tan
• Type 2. White skin that burns easily and tans with difficulty
• Type 3. White skin that may burn, but tans easily
• Type 4. Light brown or olive skin that hardly burns and tans easily
• Type 5. Brown skin that does not burn often and tans easily
• Type 6. Black skin that is very unlikely to burn and becomes darker with UV radiation exposure (10)

Did you know? Individuals with dark skin tones absorb more UVB radiation in the melanin of their skin and require more sun exposure in order to produce the same amount of vitamin D as individuals with light skin tones. (12)(14)(15)

What is sunscreen?

A topical cream applied to the skin, the purpose of sunscreen is to shield the skin from ultraviolet (UV) rays and their potential harmful effects, including sunburn, skin cancer, and accelerated skin aging. (7) A sunburn is a radiation burn to the skin caused by overexposure to the sun’s UV rays or light from indoor tanning beds. (7)

How long does sunscreen last?

If you wear sunscreen, it should be applied to the face and body 15 minutes before going outside and reapplied every two hours. (19) If you’re sweating or getting wet, you should reapply sunscreen more often. Water-resistant sunscreen can be helpful in prolonging wear, but it should be reapplied according to the instructions on the bottle. (19)

What does SPF mean?

Sunburn protection factor (SPF) refers to a measure of protection of sunscreen from UVB rays before an individual’s skin begins to burn. (6) A higher SPF sunscreen value marginally increases protection from UVB rays. For example, an SPF 15 sunscreen can block 94% of UVB rays, and an SPF 30 sunscreen can block 97% of UVB rays. (7)

When shopping for sunscreen, there are some important considerations to keep in mind. SPF ratings measure for UVB radiation protection only, so it’s important to look for a sunscreen that includes a broad spectrum of protection against both UVB and UVA rays. (6)

Additionally, the testing methods that are used to determine a product’s SPF may be unreliable. (6) The test requires an evaluator to determine a change in skin redness in a small group of human participants who are exposed to UV light in a lab setting. Depending on the participant’s skin color, the evaluator, and the testing instruments used, results may vary. (6)

The Environmental Working Group (EWG) also warns that using sunscreens with high SPF ratings (above 50 SPF) can lead to a false sense of security, more time spent outdoors in the sun, fewer reapplications, and more sun damage and cases of skin cancer as a result. (6) The EWG suggests that SPF values between 30 and 50 offer appropriate protection. (6)

Sunscreen should be applied to the face and body 15 minutes before going outside and reapplied every two hours. (19)

Why is sunscreen important?

Sunscreen is important because it protects the skin from UV radiation and plays a role in preventing skin cancers, sunburn, and increased skin aging. (19)

May prevent sunburn

Sunscreen helps prevent sunburns caused by UVB rays. (10) Duration and intensity of sun exposure are the main risk factors for sunburn. (10) Skin color type, UV index (sun intensity), ozone depletion, and altitude levels are also factors that affect the severity of a sunburn. (10) Results from a 2015 cross-sectional study that included over 31,000 U.S. adults determined that according to survey results, 34% of participants had had at least one sunburn in the last year, and sunburns were more common in individuals with pale or white skin types. (10)

Did you know? The amount of times someone has been sunburned is directly related to their risk of developing skin cancer. (10)

May prevent skin cancer

More than three million Americans and 80,000 Canadians receive a skin cancer diagnosis each year, which may be caused by exposure to either UVB rays, UVA rays, or a combination of both. (6)(17) Artificial indoor tanning beds dramatically increase skin cancer risks and should be avoided. (6)

Researchers continue to examine the relationship between sunscreen use and instances of skin cancer. An Australian study that instructed over 1,500 participants to apply sunscreen either daily or discretionarily for five years demonstrated that regular application of sunscreen may reduce future incidences of melanoma skin cancer. (9)

May prevent other skin damage

Exposure to UVA and UVB rays can damage skin cells and DNA and may advance skin aging. Ensure that your sunscreen has proper UVA protection in addition to UVB protection (broad-spectrum protection). A study that evaluated the efficacy of facial sunscreen to improve photodamage (sun damage to skin) determined that the daily application of sunscreen to the face may reverse signs of sun damage and prevent future damage to the skin. The study included 32 participants who applied a broad spectrum SPF 30 sunscreen to their face every day for one year. Dermatologist and self evaluations were measured at baseline and again consistently throughout the study period, and results demonstrated that clarity, texture, and pigmentation of the skin were improved. (16)

Physical vs. chemical sunscreen

Physical and chemical sunscreens are the two main types of sunscreen available. But how does sunscreen work? Physical sunscreens reflect the sun’s rays and act as a physical barrier, while chemical sunscreens absorb the sun’s rays. (20)

This table highlights the differences between physical and chemical sunscreens.

Physical sunscreen

Physical sunscreen, often referred to as inorganic or natural sunscreen, is mineral-based and works primarily by scattering and reflecting UV radiation. (20) Examples of active ingredients (ingredients that provide UV protection) in physical sunscreen include zinc oxide and titanium dioxide. Natural sunscreen consistency tends to be thick and an opaque white color, which may be cosmetically unappealing. (20) Zinc oxide protects against UVA1 rays and titanium dioxide protects against both UVA2 and UVB rays. (7)

Zinc oxide and titanium dioxide in sunscreen provide sun protection and don’t pose any major risks to health. (6)(18)(19) Mineral-based sunscreens may be manufactured using nanosized versions of these minerals in order to make them more stable and spreadable. Although there is no evidence to suggest that these smaller minerals penetrate the skin, inhaling or ingesting them (e.g., from lip balms) may pose some health risks, including cell damage, and more research is needed in this area to confirm their safety. (6)

Did you know? Aerosol sunscreen is sunscreen that sprays easily from a bottle but may not offer proper sun protection if it doesn’t sufficiently coat the skin. The FDA has recommended that spray sunscreens be tested to ensure they cannot cause irreversible damage to the lungs from inhalation. (6)

Natural sunscreen may also contain protective secondary ingredients, including antioxidants, osmolytes (molecules that maintain hydration and the integrity of cells in stressful conditions), and DNA repair enzymes that protect the skin from damage. (7) Examples of antioxidants ingredients in sunscreen include vitamin E, vitamin C, silymarin, green tea polyphenols. (7)

Silica and dimethicone (a silicone-based polymer) are often included as a coating ingredient to help stabilize titanium dioxide and zinc oxide in order to ensure effectiveness during photochemical reactions (when light is absorbed by the molecules of a substance). (7) Because these stabilizing ingredients are necessary in order to ensure that a physical sunscreens offers appropriate protection, the EWG encourages stricter guidelines on the types of zinc oxide and titanium dioxide used in physical sunscreens. (6)

The effectiveness of a physical sunscreen is determined by its reflective index which includes factors such as film thickness, particle size, and dispersion. (7) The higher the reflective index, the more effective the UV filter. Smaller particles make the sunscreen easier to spread onto the skin, but they may be a risk factor for skin absorption. A thicker coating of physical sunscreen increases the degree of reflection. (7)

Chemical sunscreen

Chemical sunscreen, sometimes referred to as organic-based sunscreen, absorbs the sun’s UV rays and converts them into heat. (20) The chemical structure of the sunscreen ingredients allow for high energy UV rays to be absorbed, and reduce the degree to which they can penetrate the skin. (7)(8) The wavelength that a chemical sunscreen will absorb varies depending on the ingredients. Many chemical sunscreens offer broad-spectrum protection, while others don’t. (7)

The EWG has identified a number of active ingredients commonly included in chemical sunscreens that may pose a risk to health, including:

• Avobenzone
• Homosalate
• Octinoxate
• Octisalate
• Octocrylene
• Oxybenzone (6)

Chemical sunscreen ingredients may cause allergic reactions, penetrate the skin, and act as endocrine disruptors in the body. Endocrine disruptors are chemicals that mimic the effects of hormones in the body, prevent hormones from binding to receptors, and are linked to reproductive, neurological, developmental, immune-system, and other problems. (5)

Did you know? In the United States, sunscreen is classified as an over-the-counter non-prescription drug. (7)

Sunscreen ingredients

The table below includes active ingredients that are present in many sunscreens and their corresponding level of safety to health according to the EWG and in vitro studies. (6) The U.S. Food and Drug Administration (FDA) considers the chemical sunscreen ingredients included in the table acceptable (19) and is set to propose new sunscreen regulations in the fall of 2021. Lastly, the FDA recognizes zinc oxide and titanium dioxide as safe and effective sunscreen ingredients. (6)

This table shows the active ingredients in sunscreens and their level of safety to health according to the EWG’s 2021 sunscreen report. (6)

For guidance on choosing a safe sunscreen that fits your needs, check out the EWG sunscreen list of brands here.

Additional sun protection habits

Sunscreen alone is not sufficient to protect against skin cancer and skin damage. (6) The following methods should be used alongside sunscreen:

• Seek out shaded areas.
• Spend less time in the sun during peak hours (10 am to 4 pm). (10)
• Wear a hat with a large brim.
• Wear loose-fitting colored clothing.
• Wear sunglasses with UV protection. (7)

Wearing a hat and sunglasses are important for sun protection.

The bottom line

Utilizing a broad-spectrum sunscreen in addition to practicing other sun safety techniques can help prevent sunburn, accelerated skin aging, and the risk of developing skin cancer. Natural sunscreen is a physical sunscreen that works by reflecting the sun’s rays and acts as a physical barrier. Natural sunscreen contains zinc oxide and titanium dioxide, two active ingredients that are considered safe and effective, making it a suitable alternative to chemical sunscreen.