What's Really in Your Sunscreen? A Cosmetic Chemist Breaks It Down
For this Deep Dive, Sunscreen Ingredients Explained: Safety, Absorption, and How Modern Sunscreens Work, Trina Renea sat down one-on-one with cosmetic ingredient guru Rebecca Gadberry to go beyond the basics of our earlier sunscreen episodes and get into the actual chemistry — what's in the bottle, how it behaves on skin, and which ingredient controversies actually hold up to scrutiny.
"Natural" Sunscreen Doesn't Really Exist
Rebecca opened with a myth worth retiring: there is no sunscreen ingredient approved for U.S. products that qualifies as truly natural, not even the mineral options. Zinc oxide and titanium dioxide are minerals, but they're chemically altered in a lab to make them more effective and less irritating than they'd be in their raw form. "Different than we find in nature," as Rebecca put it. It's a useful reframe for anyone choosing a mineral sunscreen under the assumption that it's unprocessed.
Do Sunscreen Ingredients Actually Get Into Your Bloodstream?
Trina asked the question a lot of people are quietly wondering: is any of this getting absorbed? Rebecca explained that nanoparticle zinc oxide — engineered to disappear invisibly on skin — is small enough to be picked up in the bloodstream, while titanium dioxide is generally too large a molecule to penetrate. Trina connected the dots on why this matters: "the reason we used mineral sunscreens was because they sat on the surface and were too big a molecule to penetrate... now they've made them so small to try and make them disappear on the skin." Rebecca's reassurance: detection in the blood isn't automatically dangerous. Ingredients like this are typically excreted through urine rather than retained in the body.
The Coral Reef Debate, Revisited
Trina and Rebecca also revisited the sunscreen-and-coral-reefs controversy. Rebecca explained that the original research showing harm was conducted in confined aquarium settings, not the open ocean, and pointed instead to climate change, agricultural runoff, and overfishing as the bigger, better-documented threats to coral health. Whether or not sunscreen chemicals play a meaningful role remains, in her view, scientifically unresolved.
Why Silicones Are in Your Sunscreen — and What Antioxidants Are Doing There
Rebecca also explained the practical role of silicones like dimethicone: they help sunscreen spread evenly across skin, which actually increases effective SPF by preventing gaps in coverage. And she made the case for choosing a sunscreen with antioxidants layered in — since chemical sunscreens can generate free radicals as they convert UV energy to heat, ingredients like stabilized vitamin C and tocopherol help neutralize that byproduct.
Listen to the full episode → Facially Conscious
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The Skin Master
Co-host | When Trina Renea became an esthetician she realized the key to success was lifelong learning - a goal that sets her apart from most skin care practitioners.
For over 30 years, she’s explored the fields of cosmetic chemistry, medical esthetics, dermatology, and plastic surgery, becoming an expert in a wide expanse of professional skin care brands, equipment, and treatments. She is a member of the Society of Cosmetic Chemists with three certifications in cosmetic sciences from UCLA and continues to attend spa, medical, esthetic, and scientific conferences worldwide.
Now considered a skin master due to her broad expertise, Trina is a consultant to the Southern California beauty industry and medical esthetic community, selecting and training staff, developing treatments, guiding product selection, and helping professionals best serve their clients.
In 2004, she founded the Facial Bungalow, a clinical spa offering advanced skin care technologies where she continues to work one-on-one with clients to this day. In 2008 she created Trina Renea Skincare.
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