A Guide to Sunscreen Selection

Elisabeth A. George, BA

Daily sunscreen use has been recommended by the Food and Drug Administration (FDA) and the American Academy of Dermatology (AAD) for decades. Recently, sunscreen use has become a controversial topic. There are questions about whether certain active ingredients in sunscreens may adversely affect human health and the environment. There are also concerns regarding contamination of commercial sunscreens, after many companies recalls batches of affected products in July 2021. The following article explains the differences between physical, chemical, and tinted sunscreens and provides tips for protecting skin of color.

What are sunscreens?

Sunscreens are topical formulas that contain active ingredients that can absorb or reflect ultraviolet (UV) radiation. Sunlight is the most common form of UV radiation. The spectrum of UV radiation is divided into three categories – UVA, UVB, and UVC – based on wavelength. Each type of UV radiation affects skin differently. For example, UVA radiation can penetrate skin deeper than UVB. While UVA exposure contributes to early photoaging, UVB exposure leads to sunburns and stimulates vitamin D3 synthesis. Both UVA and UVB can damage skin cells and increase the risk of skin cancer. UVC radiation is absorbed by Earth’s ozone layer, so humans are not exposed to this type of UV radiation from sunlight.

What is sun protection factor?

Commercially available sunscreens are assigned a sun protection factor (SPF) that can be found on the product label. SPF quantifies the degree of sunburn protection that a sunscreen provides. In other words, it is a measure of the amount of UV radiation that is necessary to produce a sunburn after sunscreen application. As SPF increases, a higher degree of UV protection is provided. For example, SPF30 allows 1/30 (or 3.3%) of ambient UV radiation to penetrate skin. This means that 29/30 (or 96.7%) of UV radiation is blocked. On the other hand, SPF50 allows 1/50 (or 2.0%) of ambient UV radiation to penetrate skin, which equates to blocking 98% of UV radiation. Currently, the AAD recommends daily use of a broad-spectrum, water-resistant sunscreen with SPF 30 or higher. “Broad-spectrum” refers to the fact that the sunscreen protects against both UVA and UVB radiation. “Water-resistant” sunscreens can protect skin while swimming or sweating for 40 minutes, while “very water-resistant” formulas provide up to 80 minutes of protection.

What is physical sunscreen?

Sunscreens are divided into two broad categories – physical or chemical – depending on the type of active ingredients included in the formula. These active ingredients are the compounds that protect your skin from UVA and UVB radiation. For this reason, they are sometimes called “UV filters”. Physical sunscreens, also referred to as mineral sunscreens, contain zinc oxide and/or titanium dioxide as active ingredients. These mineral UV filters act as a physical barrier and reflect UV radiation. In this way, mineral UV filters prevent UV rays from penetrating skin. Historically, mineral sunscreens have been known to leave an unsightly white or gray cast on skin of color. However, many new formulas feature smaller “nanonized” zinc oxide or titanium dioxide particles. These nanonized ingredients are also referred to as “nanoparticles” or “nanosized particles”. Using smaller particles of zinc oxide or titanium dioxide leads to a relatively transparent final product that is compatible with darker skin tones.

What is chemical sunscreen?

Chemical sunscreens commonly include a combination of active ingredients such as avobenzone, oxybenzone, octinoxate, octocrylene, octisalate, among others. When chemical sunscreen is applied, these chemical UV filters are absorbed. Later, when the skin is exposed to UV radiation, the active ingredients absorb the UV radiation and convert it into thermal energy (heat). This reaction may produce free radicals as a byproduct, which are damaging to skin. Therefore, many brands add antioxidants such as vitamins C and E to chemical sunscreen formulas. These antioxidants effectively neutralize any free radicals that are produced before they can damage the skin. Applying antioxidant-containing serums or moisturizers prior to sunscreen is often recommended for additional free radical protection. Of note, there are many common environmental exposures that can increase free radical production, including air pollution, UV radiation, and cigarette smoke; chemical sunscreen is not the only free-radical inducing agent.

What is tinted sunscreen?

Sunlight is common source of both UV radiation and visible light exposure. Visible light can harm skin by inducing free radical production, DNA damage, and impair cell function, leading to premature skin aging. Blue light is a type of visible light that is especially damaging to skin. Electronics such as smartphones, computers, and televisions are common sources of blue light exposure. Compared to UV radiation, blue light may lead to darker pigmentation that takes a longer time to fade.

Physical and chemical UV filters protect skin from UV radiation; however, they do not provide visible light protection. Therefore, people with melasma and post-inflammatory hyperpigmentation may experience disease exacerbation following sun exposure, even if they apply physical or chemical sunscreens. Tinted sunscreens include visible light filters in addition to UV filters. Examples of visible light filters include iron oxides and pigmentary titanium dioxide, which is titanium dioxide that is not nanosized. Remember that many new untinted physical sunscreens contain nanonized titanium dioxide particles so that the formula does not leave a white/gray cast. In contrast, tinted sunscreens contain various quantities of yellow, red, and black iron oxide with pigmentary titanium dioxide and UV filters. This results in a wide color range of tinted formulas that can match virtually any skin tone. These tinted formulas can boost skin color, even skin tone, and conceal blemishes and discoloration, while providing essential UV radiation and visible light protection.

Which type of sunscreen should I use?

This is a personal choice that can be further discussed with a board-certified dermatologist. Tinted sunscreens are a safe and effective option for people with skin conditions that are triggered by visible light exposure, such as melasma or post-inflammatory hyperpigmentation. People with sensitive skin may develop rashes or irritation from chemical sunscreens. In these cases, mineral sunscreen may be a preferable option. For people with acne and/or oily skin, non-comedogenic, oil-free sunscreen formulas are generally recommended. The table below highlights some common issues that people of color may experience when incorporating sunscreen into their daily regimen and offers potential solutions.

In January 2021, legislation was put into effect in Hawaii that banned sales of chemical sunscreens that contain oxybenzone or octinoxate because these chemicals may be implicated in coral reef damage. Accordingly, many brands have developed chemical sunscreens that do not include these active ingredients. Often these environmentally friendly sunscreens include “reef-safe” on the product label.

As of August 2021, zinc oxide and titanium dioxide are the only two active ingredients in sunscreens that have received a GRASE rating by the FDA, which stands for generally recognized as safe and effective. The FDA is currently requesting more industry testing to determine whether active ingredients that are included in chemical sunscreens should qualify for GRASE ratings. Further testing has been requested for avobenzone, oxybenzone, dioxybenzone, sulisobenzone, octinoxate, cinoxate, octocrylene, octisalate, homosalate, ensulizole, meradimate, and padimate O.

Sunscreen application tips: 

• Obtain water-resistant, broad-spectrum formulas with SPF30 or higher
• Remember that sunscreen should be applied to every area of skin that is not covered by clothing. Commonly neglected areas include the ears, hands, feet, and neck.
• Use about 1 ounce, which is about a shot glass, of sunscreen to cover the entire body
• Use a ½ teaspoon of sunscreen to cover the face and neck
• Remember that even water-resistant sunscreens and high-SPF sunscreens should be reapplied directly after swimming or sweating.
• Remember that, regardless of SPF, sunscreen should be reapplied every 2 hours when you are outdoors.

References:

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