Sunscreen: Everything You Need to Know

Health

25 June 2020

Protect yourself from the sun that gives us vitamin D. Protect yourself from the sun that can also contribute to skin cancer. Worry about a possible vitamin D deficiency while reading conflicting headlines about sunscreen ingredients. It is easy to get confused.

Whenever someone tells me that something is absolutely essential for my survival, I instinctively become cautious. I have never been a fan of the idea that one size fits all. Need protection from the sun? Buy sunscreen and put it on. Problem solved? Not quite. So should we use sunscreen or not?

Зміст

Getting to Know Ultraviolet Radiation

Types of Ultraviolet Radiation

Ultraviolet radiation is divided into three types based on wavelength: UVA, UVB, and UVC. The shorter the wavelength, the more harmful it is, but the less deeply it penetrates the skin. The most harmful type, UVC, is completely blocked by the Earth’s atmosphere.

The atmosphere also filters most UVB radiation, although some still reaches the upper layers of the skin. While the ozone layer provides important protection against UVB, its depletion in certain regions has historically increased ultraviolet radiation levels at the Earth’s surface. UVB is primarily responsible for sunburns, plays a role in tanning, and contributes significantly to the development of skin cancer. It is also the type of radiation that triggers vitamin D production in the body.

UVA rays account for approximately 95% of the ultraviolet radiation that reaches the Earth’s surface. They penetrate deeper layers of the skin and are responsible for the immediate tanning effect. They contribute to skin aging and wrinkle formation and can also pass through glass. It is now well established that UVA also plays a role in the development of skin cancer.

What Influences UV Exposure?

The intensity of ultraviolet radiation depends on several factors:

Season and time of day (UV levels peak during summer months and around midday);
Latitude (UV radiation is stronger closer to the equator);
Altitude (the higher above sea level, the less UV radiation is absorbed by the atmosphere);
Reflection from surfaces (water, grass, and soil reflect less than 10% of UV radiation, sand about 15%, sea foam around 25%, and snow up to 50%);
Clouds and haze (while clouds generally reduce UV exposure, thin clouds can sometimes increase it, which is why protection is recommended even on overcast days).

Sunburns

The more sunburns we experience throughout life, the higher our risk of skin cancer. Children’s skin is especially sensitive, and sunburns should be avoided whenever possible. The number of burns a person can sustain before serious damage occurs varies greatly and depends on genetics, family history, skin type, cumulative sun exposure, and the severity of individual burns. The more easily your skin burns, the greater your risk.

Understanding Sunscreen

SPF

The first thing most people notice on a sunscreen bottle is SPF (Sun Protection Factor). SPF measures protection against UVB radiation—the type primarily responsible for sunburn—but it does not indicate protection against UVA rays.

For that reason, dermatologists recommend choosing products labeled “broad spectrum,” meaning they protect against both UVA and UVB radiation.

SPF 30 is generally recommended. If you expect significant sweating or water exposure, water-resistant products may provide protection for about 40 minutes in water, while very water-resistant formulas are tested for up to 80 minutes.

For sunscreen to work as intended, it should be applied generously—approximately 2 mg per square centimeter of skin—and reapplied every two hours. Most people use only one-quarter to one-half of the recommended amount and often forget to reapply it altogether.

SPF values are not linear:

SPF 15 blocks approximately 93% of UVB rays;
SPF 30 blocks approximately 97%;
SPF 50 blocks approximately 98%.

Chemical and Mineral Sunscreens

Some sunscreens rely on chemical UV filters, while others create a physical barrier using mineral ingredients such as zinc oxide or titanium dioxide.

Certain sunscreen ingredients continue to be studied, particularly regarding their long-term effects on human health and the environment. However, the sunscreen products approved by regulatory authorities are generally considered safe when used as directed.

Forms of Sunscreen

Creams: best for dry skin and facial use;
Lotions: lighter and less greasy, commonly used on the body;
Gels: suitable for hairy areas;
Sticks: useful around the eyes;
Sprays: convenient, especially for children, although care should be taken to avoid inhalation.

Skin Cancer

The three major forms of skin cancer are basal cell carcinoma, squamous cell carcinoma, and melanoma. When detected early, all are highly treatable. Managing sun exposure can help reduce risk.

The relationship between sunlight and melanoma is more complicated than the simple formula of “more sun equals more risk.” The pattern of exposure, frequency of sunburns, genetics, and lifestyle all play important roles.

As dermatologist Richard Weller has noted:

When you spend your days treating patients with devastating melanomas, it is natural to focus on prevention. But we also need to remember the bigger picture. Orthopedic surgeons do not advise patients to avoid exercise simply because exercise can occasionally lead to knee injuries.

Throughout human evolution, people developed natural defenses against ultraviolet radiation through melanin production. As populations migrated farther from the tropics, skin adapted to changing environmental conditions. Seasonal patterns of sun exposure likely allowed for a more gradual adaptation than many people experience today. The modern pattern of spending most of the year indoors and then suddenly exposing the skin to intense sunlight during vacations may present its own risks.

For many years, studies examining sunscreen and melanoma produced mixed results. Today, however, the overall evidence suggests that sunscreen helps reduce the risk of certain skin cancers and protects against photoaging. No sunscreen provides complete protection, which is why the most effective strategy combines sunscreen with protective clothing, hats, sunglasses, and sensible sun habits.

Potential Risks and Areas of Ongoing Research

Some aspects of sunscreen safety continue to be studied:

Titanium dioxide and zinc oxide nanoparticles are considered safe for use on intact skin, although inhalation exposure in aerosol products remains an area of research;
PABA-based products and certain benzophenones may cause skin irritation in some people;
Octinoxate and oxybenzone have demonstrated hormone-like effects in laboratory and animal studies, but there is currently no convincing evidence that normal sunscreen use causes hormonal disorders in humans;
Avobenzone, oxybenzone, octocrylene, ecamsule, and some other ingredients can be absorbed into the bloodstream. Their presence in blood does not automatically indicate harm, but long-term effects continue to be studied;
Some products contain vitamin A derivatives, and questions remain about their suitability during direct sun exposure;
High temperatures and prolonged storage in direct sunlight may reduce the effectiveness of certain formulations;
Oxybenzone and some other UV filters have been implicated in coral reef damage, leading to restrictions in some regions, including Hawaii;
In theory, extremely thorough and constant sunscreen use could reduce vitamin D production, although most real-world studies have not found a significant effect on vitamin D levels.

Vitamin D

In practice, sunscreen often does not block vitamin D production to the extent one might expect. This is partly because people rarely apply sunscreen perfectly and partly because most individuals still receive some ultraviolet exposure despite using protection.

Vitamin D supplementation was once viewed as a potential preventive measure for a wide range of diseases. However, large reviews and randomized controlled trials have shown that, for most healthy individuals without a documented deficiency, the benefits are considerably more modest than initially hoped. For people with vitamin D deficiency or specific medical indications, supplementation can still be beneficial.

In 2005, the Australasian College of Dermatologists officially emphasized that ultraviolet radiation has both beneficial and harmful effects on health, and that recommendations should balance risks and benefits.

So How Should We Protect Ourselves From the Sun?

Consider your skin type, genetics, lifestyle, and environment;
Limit sun exposure during peak hours, especially between 10 a.m. and 4 p.m.;
Gradually increase sun exposure rather than relying on occasional intense exposure;
Remember that water, sand, grass, and snow can reflect sunlight and increase UV exposure;
Wear protective clothing, hats, and sunglasses;
Use sunscreen when appropriate, preferably SPF 30 or higher and broad-spectrum protection;
Support overall skin health through a balanced diet rich in vegetables, fruits, omega-3 fatty acids, and antioxidant-containing foods.

Foods such as tomatoes, watermelon, grapefruit, pomegranate, and other red fruits contain lycopene, an antioxidant that some studies associate with increased resistance to ultraviolet damage. Fatty fish, flaxseed, and chia seeds provide omega-3 fatty acids, while tea and dark chocolate contain compounds with antioxidant and anti-inflammatory properties.

Sunlight affects more than vitamin D production. It plays a role in regulating circadian rhythms, mood, and a range of physiological processes. Researchers continue to investigate its possible links to cardiovascular health, inflammation, and various diseases. Many of these mechanisms remain active areas of scientific debate.

Sunscreen: Everything You Need to Know