WHAT’S THE DIFFERENCE BETWEEN CHEMICAL AND PHYSICAL SUNSCREENS?
Chemical sunscreens protect the skin from ultraviolet (UV) rays by absorbing radiation and converting it into heat energy, while physical sunscreens provide a physical barrier that deflects the sun’s rays so that they aren’t absorbed into the skin. Both types of sunscreen are effective at preventing sunburn and reducing risk of premature skin aging and skin cancer, but based on an individual’s skin type, age, outdoor activities, and any special skin conditions, one type of sunscreen might be preferable over the other.1
Chemical sunscreens aren’t as thick as physical sunscreens, making them easier to apply. They have greater staying power, which makes them preferable for swimmers and sweaty athletes. However, chemical sunscreens must
be applied 30 minutes before sun exposure in order to adequately absorb into the skin to provide protection. They also absorb heat into the skin, so they are not ideal for individuals with skin conditions that are exacerbated
by heat, such as rosacea and acne. In addition, newer research suggests that chemical sunscreen ingredients, such as oxybenzone, are damaging to oceanic ecosystems, including reefs and marine wildlife.1,2
When applying a sunscreen that uses an active ingredient such as zinc oxide or titanium oxide, a physical barrier is formed as soon as the sunscreen is applied, so there’s no wait time. Physical sunscreens deflect heat away from the skin, so they’re optimal for those with sensitive skin or conditions like acne or rosacea.
In addition, they’re less likely to clog pores than chemical sunscreens and are usually used in noncomedogenic facial sunscreens. However, since physical sunscreens sit on top of the skin, they can leave a white cast that some users find undesirable, especially when being used on darker skin tones. In addition, physical sunscreens can be rubbed off easily and are less resistant to sweat and swimming than chemical sunscreens.1
WHICH ONE IS RIGHT FOR ME?
For days when sun exposure is limited to a few minutes here and there, a sun protection factor (SPF) of 15 is sufficient. For extended, intense sun exposure
(i.e., hiking, trips to the beach or pool, sporting events), SPF 30 or above is preferable. Whether you choose a physical or chemical sunscreen, your choice should have broad spectrum protection, meaning it protects against both UVA and UVB radiation.3
Young children and babies, who tend to have more sensitive skin than adults, and adults with sensitive, allergy-prone skin and/or skin conditions such as acne or rosacea are more likely to experience adverse reactions with chemical sunscreens.3 Physical sunscreens are gentler on the skin and less likely to cause irritation or exacerbate existing skin conditions, making them the better choice for these individuals.3 People with acne or rosacea should also avoid sunscreens containing alcohol, preservatives, or fragrances, due to their tendancy to trigger flare-ups and breakouts. Additionally, topical acne treatments, such as salicylic acid or retinol/retinoid products, can increase the skin’s sensitivity to the sun; thus, people using these products should also use an effective sunscreen that can be applied daily.3
People with melasma, fair skin, and/or a history of skin cancer require extra protection and should use a daily sunscreen containing SPF 30 or more and reapply every two hours.3
People with darker skin tones might wish to avoid physical sunscreens
due to the white streaks or white cast these products tend to leave on the skin; darker-skinned individuals might be more satisfied with a chemical sunscreen, which will go on clear and absorb into the skin without streaking.3
1. Lankerani L. Physical Sunscreen vs. Chemical 3. Sunscreen. Westlake Dermatology site. 26 Jun
2018. https://www.westlakedermatology.com/ blog/chemical-sunscreen-vs-physical-sunscreen- which-is-better/. Accessed 31 May 2019.
2. National Ocean Service National Oceanic and Atmospheric Administration site. Skincare chemicals and coral reefs. 20 May 2019. https:// oceanservice.noaa.gov/news/sunscreen-corals. html. Accessed 31 May 2019.
3. Saini R, Szemplinski A. How to choose the right sunscreen for your skin type. Skin Cancer Foundation site. https://www.skincancer.org/ prevention/sun-protection/sunscreen/choosing. Accessed 2 Jun 2019. NHR
Are Sunscreen Ingredients Absorbed into the Bloodstream?
Yes, but the American Academy of Dermatology (AAD) is urging alarmed beach goers not to jump to conclusions.
Investigators in small study1 of 24 people measured blood levels of four active ingredients that are used in sunscreens: avobenzone, oxybenzone, octocrylene, and ecamsule. The study found that, under maximal use conditions, blood concentrations of these ingredients exceeded the threshold established by the United States Food and Drug Administration (FDA) to waive some nonclinical toxicology studies for sunscreens.
While the AAD acknowledged this study as an important step in learning more about the many active ingredients that are currently used in commercially available sunscreen, members emphasized that this new study is a small, pilot study that only determined that these sunscreen ingredients are absorbed into the body, but did not investigate what effects, if any, these absorbed ingredients have on human health.2 Citing skin cancer as the most common cancer in the United States, AAD members urge citizens to continue practicing recommended skin cancer prevention strategies, including using a broad spectrum sunscreen on sun-exposed skin not covered by hats or clothing.
It is important to note that all four of the tested ingredients were chemical, as opposed to physical, sunscreen ingredients. Out of 16 active ingredients currently used in marketed sunscreen products, two of these ingredients—zinc oxide and titanium oxide—both of which are used in many of the widely available physical sunscreen products, are generally regarded by qualified experts to be safe and effective for their intended uses, based on published, well-controlled clinical investigations.3
- Matta MK, Zusterzeel R, Pilli NR. Effect of sunscreen application under maximal use conditions on plasma concentration of sunscreen active ingredients: a randomized clinical trial. JAMA. 2019 May 6. Epub ahead of print.
- American Academy of Dermatology comments on recent study on absorption of sunscreen ingredients [news release]. Rosemont, IL: Statement from AAD President George J. Hruza, MD, MBA, FAAD; 6 May 2019. https:// www.aad.org/media/news-releases/study-sunscreen-ingredients. Accessed 2 Jun 2019.
- FDA advances new proposed regulation to make sure that sunscreens are safe and effective [news release]. U.S. Food and Drug Administration; 21 Feb 2019. https://www.fda.gov/news-events/press-announcements/fda- advances-new-proposed-regulation-make-sure-sunscreens-are-safe-and-effective. Accessed 2 Jun 019. N
FDA-approved sunscreen ingredients in the United States
- UVA absorbers: avobenzone, ecamsule (Mexoryl SX), meradimate
- UVB absorbers: para-aminobenzoic acid (PABA), cinoxate, ensulizole, homosalate, octocrylene, octinoxate, octisalate, padimate 0, trolamine salicylate
- UVA and UVB absorbers: dioxybenzone, oxybenzone, sulisobenzone PHYSICAL SUNSCREENS
• UVA and UVB physical sunscreens: titanium oxide, zinc oxide
SOURCE: Saini R, Szemplinski A. How to Choose the Right Sunscreen for Your Skin Type. Skin Cancer Foundation site. https://www.skincancer.org/ prevention/sun-protection/sunscreen/choosing. Accessed 31 May 2019. NHR