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COSMETIC MEDICINE

in the bloodstream is not new infor-
mation. In the late 90s, a similar
finding was shown by Hayden et. al.
2
and published in the Lancet. Since
then, the FDA, which regulates sun-
screens in the U.S. as over-the-
counter drugs, has issued guidelines
that encourage sunscreen maximal
use clinical trials to demonstrate sys-
temic absorption of active ingredi-
ents and to see if that is above 0.5
ng/mL; if systemic absorption is
more than this threshold, the FDA
requires further studies on toxicol-
ogy. Thus, the study by Matta et. al.
supports the need for further inves-
tigations to determine the clinical
significance of the findings.
At this point, showing that active ingredients are absorbed sys- proliferation in brands and formulations that I think most people
temically does not imply toxicity. Little is known about the toxi- can find one that works for them,” says Dr. Siddiqui.
cities of sunscreen ingredients. High systemic levels of Protecting the skin from the sun is more than just sunscreen,
oxybenzone are thought to be linked to hormonal changes in however. Avoiding sun exposure at peak hours between 10 a.m.
3
males, but more research focusing on such effects is needed. and 4 p.m. checking the UV index, which offers a snapshot of
In addition, it is important to know that the study investigators how likely one is to burn based on the amount of UVB light,
clearly stated their results do not indicate that individuals should re- wearing wide-brimmed hats, sunglasses, long sleeve shirts, and
frain from using sunscreen. The authors also acknowledge the lim- staying in shaded areas as also important to help keep skin looking
itations of their study — it was conducted in indoor conditions younger and healthier.
without exposure to heat, sunlight, and humidity, which may alter “If sunscreens are not a realistic part of someone’s routine, I en-
the rate of absorption of sunscreen. Furthermore, the study was courage patients to purchase sun protective clothing,” says Dr. Sid-
performed with healthy adult volunteers, which leaves room for in- diqui. “I just bought an SPF 50 shawl myself!”
vestigating systemic absorption of sunscreen active ingredients in
children and in people with chronic skin conditions. Resources
With all of this, it is important to know that dermatologist still 1 Matta, Murali K., et al. “Effect of sunscreen application under
recommend using sunscreen on a regular basis. There are two kinds maximal use conditions on plasma concentration of sunscreen
of sunscreen — chemical sunscreens that absorb sunlight and phys- active ingredients: a randomized clinical trial.” JAMA (2019).
ical sunscreens that deflect sunlight. The former can contain oxy- 2 Hayden, Cameron GJ, Michael S. Roberts, and Heather AE Ben-
benzone, avobenzone, octisalate, octocrylene, homosalate, or son. “Systemic absorption of sunscreen after topical applica-
octinoxate as their active ingredients, and they tend to be easier to tion.” The Lancet 350.9081 (1997): 863-864.
apply to the skin; the latter contain titanium dioxide, zinc oxide, or 3 Janjua, Nadeem Rezaq, et al. “Systemic absorption of the sun-
both, and they are recommended for sensitive skin. The FDA has screens benzophenone-3, octyl-methoxycinnamate, and 3-(4-
proposed that titanium dioxide and zinc oxide are “generally recog- methyl-benzylidene) camphor after whole-body topical
nized as safe and effective.” Therefore, people worried about sys- application and reproductive hormone levels in humans.” Journal
temic exposure of sunscreen ingredients can consider this when of Investigative Dermatology 123.1 (2004): 57-61.
making their selection.
“Physical blockers have been known to leave a white cast or feel Pavela G. Bambekova is a medical student at UT Health San Antonio.
greasier than their chemical counterparts, but there’s been such a

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