The great sunscreen ingredient debate

In a commentary issued on May 6, the Food and Drug Administration stated that “with sunscreens now being used with greater frequency, in larger amounts, and by broader populations, it is more important than ever to ensure that sunscreens are safe and effective for daily, lifelong use.” The statement coincided with the publication of the randomized study, “Effect of sunscreen application under maximal use conditions on plasma concentrations of sunscreen active ingredients,” by Matta et al. of the FDA and others in JAMA (2019 May 6. doi: 10.1001/jama.2019.5586). A maximal usage trial examines the systemic absorption of a topical drug when used according to the guidelines given for the product’s maximum usage. In this study, adult participants were randomized to one of four commercially available sunscreen products: spray 1 (n = 6), spray 2 (n = 6), a lotion (n = 6), and a cream (n = 6). Two mg of sunscreen per 1 cm² was applied to 75% of body surface area four times per day for 4 days, and blood samples were collected from each individual over 7 days.

Plasma concentrations of the four active ingredients tested – avobenzone, oxybenzone, octocrylene, and ecamsule – were above 0.5 ng/mL. The FDA’s guidance for industry and proposed rule on OTC sunscreens state that active ingredients with systemic absorption at 0.5 ng/mL or higher or with possible safety concerns need to undergo further nonclinical toxicology assessment to evaluate risk of systemic carcinogenicity, developmental/reproductive abnormalities, or other adverse effects.

Absorption of some sunscreen ingredients has been detected in other studies. Despite systemic absorption, two active ingredients – zinc oxide and titanium dioxide – have been found by the FDA to be generally recognized as safe and effective. But for 12 other active ingredients (cinoxate, dioxybenzone, ensulizole, homosalate, meradimate, octinoxate, octisalate, octocrylene, padimate O, sulisobenzone, oxybenzone, and avobenzone), there are insufficient data to make a “generally recognized as safe and effective” determination; thus, more data have been requested from the manufacturers. While physical blocking sunscreens have improved in their UV-blocking ability without compromising cosmesis over the past several years, some sunscreens containing chemical blockers are able to achieve higher SPFs with good cosmesis when applied to the skin.

Our skin acts as the ultimate barrier between ourselves and the environment, and it is not uncommon for substances to be blocked, absorbed, or excreted from the skin. Absorption of an ingredient through the skin and into the body does not indicate that the ingredient is unsafe. Rather, findings such as these call for further testing and research to determine the safety of that ingredient with repeated use. Per the FDA, such testing is part of the standard premarket safety evaluation of most chronically administered drugs with appreciable systemic absorption.

In February 2019, the FDA’s proposed rule was issued to “update regulatory requirements for most sunscreen products in the United States,” with the goal of bringing OTC sunscreens “up to date with the latest scientific standards,” according to the FDA May 6 commentary. “As part of this rule, the FDA is asking industry and other interested parties for additional safety data on the 12 active sunscreen ingredients currently available in marketed products” mentioned previously. These rules are being put into place to address the “key data gap” for these 12 ingredients, which is “understanding whether, and to what extent the ingredient is absorbed into the body after topical application.”

In other previously published studies, oxybenzone, along with some other sunscreen active ingredients including octocrylene, have been found in human breast milk. In addition, oxybenzone has been detected in amniotic fluid, urine, and blood. Whether these findings have any clinical implications needs to be further assessed. Some studies in the literature have raised questions about the potential for oxybenzone to affect endocrine activity.

Another issue that has been raised is the potential impact of sunscreen on the environment, specifically, coral reefs. In July 2018, Hawaii Governor David Ige (D) signed a bill (SB 2571) that bans the sale of sunscreens containing oxybenzone and octinoxate beginning in 2021, making Hawaii the first state to ban the sale of sunscreens containing these two chemicals. Shortly afterward, the Republic of Palau and city of Key West, Fla., also took action to ban sunscreens containing chemicals potentially harmful to marine life. In Hawaii, what’s know as “reef safe” sunscreen is sold.

More research in this area is needed, but studies have linked these ingredients to harming coral by bleaching, disease, and damage to DNA, and also to decreasing fertility in fish, impairing algae growth, inducing defects in mussel and sea urchin young, and accumulating in the tissues of dolphins. According to NASA, as much as 27% of monitored reef formation have already been lost and over the following 32 years, 32% more are at risk. Reefs cover a mere 0.2% of the ocean’s floor, but it is estimated that reefs are home to and protect nearly 1 million species of fish, invertebrates, and algae.

In early May, Rep. Tulsi Gabbard (D-Hawaii) and Sen. Tim Ryan (D-Ohio) introduced legislation known as the Oxybenzone and Octinoxate Impact Study Act of 2019 (H.R. 2588) to require the Environmental Protection Agency to study the impact of those two chemicals on human health and the environment and to provide findings to Congress and the public within 18 months.

The importance of sun protection and prevention of sunburns is paramount. We know that multiple sunburn events during childhood double a child’s risk of developing skin cancer later in life, and skin cancer is the most common cancer diagnosed in the United States, with 5 million cases treated every year. One in five Americans will develop skin cancer by age 70 years.

As a Mohs and a cosmetic dermatologic surgeon, I appreciate the unquestionable protective effects of sunscreen products with regards to skin cancer, dyspigmentation, solar elastosis, and rhytids associated with photoaging. We can applaud the FDA for improving testing and regulation of OTC ingredients, including those in sunscreen. These types of studies are important and monumental in ensuring that we are utilizing the right type of ingredients to protect our patients, our oceans, and our reefs.

Shop our favorite skincare and more on Derm to Door.com!

Head back to our blog here!