Sunscreen contains two types of active ingredients: mineral filters that physically block UV rays, and chemical filters that absorb UV radiation and convert it to heat. Most products also include a base of inactive ingredients like moisturizers, stabilizers, and preservatives that hold the formula together and make it feel good on your skin. The specific mix depends on whether you’re using a mineral, chemical, or combination sunscreen.
Mineral vs. Chemical Filters
The distinction between mineral and chemical sunscreens comes down to how they protect your skin. Mineral filters, also called physical blockers, sit on the skin’s surface and work through a combination of scattering and absorbing UV light. Chemical filters are organic compounds that absorb UV radiation exclusively, converting it into small amounts of heat that dissipate from your skin.
Only two mineral filters exist: zinc oxide and titanium dioxide. These are the only sunscreen active ingredients the FDA currently classifies as safe and effective without reservation. Zinc oxide provides its strongest protection in the UVA range (around 370 nm), while titanium dioxide peaks in the UVB range (around 310 nm). Together, they cover the full UV spectrum, which is why many mineral sunscreens use both.
Chemical filters are more varied. The most common ones you’ll see on labels include avobenzone, homosalate, octinoxate, octisalate, octocrylene, and oxybenzone. Each targets a slightly different slice of the UV spectrum, so formulas typically combine several to achieve broad-spectrum protection. Avobenzone is the go-to chemical filter for UVA protection, while most of the others focus on UVB rays.
What the FDA Says About Safety
Of the 16 sunscreen active ingredients recognized by the FDA, only zinc oxide and titanium dioxide have a clean bill of health under the agency’s current review. Two older ingredients, PABA and trolamine salicylate, have been deemed not safe and effective and are essentially off the market. The remaining 12 chemical filters, including all the widely used ones like avobenzone, oxybenzone, and homosalate, sit in a gray zone: the FDA says it needs more safety data before making a final determination.
That doesn’t mean these ingredients are dangerous. It means the FDA wants additional studies, particularly on systemic absorption. In clinical trials, researchers found that chemical filters do enter the bloodstream at levels above the FDA’s safety threshold of 0.5 nanograms per milliliter. Oxybenzone showed the highest absorption by far, reaching plasma concentrations as high as 258 ng/mL when applied as a lotion. Avobenzone reached about 7.1 ng/mL. These numbers triggered the request for more data, but no sunscreen ingredient has been linked to harm in humans at real-world usage levels.
Mineral ingredients don’t raise the same concern. Zinc oxide nanoparticles, even at sizes as small as 30 to 55 nanometers, do not penetrate through the skin based on available evidence. Larger, non-nano particles are even less likely to be absorbed.
Nano vs. Non-Nano Minerals
If you’ve seen “non-nano” on a mineral sunscreen label, it refers to particle size. Nanoparticles are smaller than 100 nanometers and go on more transparently, reducing the white cast that mineral sunscreens are known for. Non-nano particles are larger and tend to leave a more visible film on the skin but are considered even less likely to be absorbed. Both forms stay on the skin’s surface and don’t enter the bloodstream, so the choice between them is mostly cosmetic.
Inactive Ingredients That Round Out the Formula
Active ingredients do the UV-blocking work, but they typically make up only a fraction of what’s in the bottle. The rest is a blend of inactive ingredients that serve specific purposes:
- Emollients and moisturizers like glycerin, shea butter, or dimethicone give the sunscreen its texture and keep your skin from drying out.
- Emulsifiers help oil-based and water-based components stay mixed instead of separating in the bottle.
- Stabilizers prevent active ingredients from breaking down in sunlight. Avobenzone is notoriously unstable on its own, so most formulas include octocrylene or other stabilizing agents to extend its effectiveness.
- Preservatives like phenoxyethanol prevent bacterial growth and extend shelf life.
- Fragrances and botanical extracts are added for scent and marketing appeal, though fragrance-free options are widely available for sensitive skin.
Some sunscreens also include antioxidants like vitamin C, vitamin E, or ferulic acid. These don’t block UV radiation directly, but they neutralize free radicals generated by sun exposure, providing a secondary layer of defense against skin damage. Vitamin E in particular can help stabilize certain UV filters, improving the product’s overall performance.
Filters Available Outside the U.S.
Sunscreens sold in Europe, Japan, South Korea, and Canada often contain UV filters that aren’t available in the United States. The Tinosorb family of filters (Tinosorb S, Tinosorb M, and Tinosorb A2B) provide both physical and chemical protection across the full UVA and UVB spectrum. Mexoryl SX, owned by L’Oréal, offers broad UVA coverage. These newer filters tend to be more photostable than avobenzone, meaning they don’t break down as quickly in sunlight.
The FDA’s approval process for new sunscreen ingredients has been notoriously slow, which is why American sunscreens still rely on the same filters that have been available for decades. If you’ve ever tried a European or Asian sunscreen and noticed it felt lighter or less greasy, these newer filters are a big reason why. They allow for thinner, more cosmetically elegant formulas while maintaining high protection levels.
Reef Safety and Banned Ingredients
Hawaii banned sunscreens containing oxybenzone and octinoxate after research linked both chemicals to coral bleaching. When coral is exposed to high concentrations of these compounds, it turns white and can eventually die. Several other coastal destinations have followed with similar restrictions.
Sunscreens labeled “reef safe” typically use mineral filters (zinc oxide and titanium dioxide) instead of chemical ones, though the term isn’t regulated and doesn’t guarantee a product is free of all potentially harmful ingredients. If you’re swimming near coral reefs, checking the active ingredients list for oxybenzone and octinoxate is more reliable than trusting front-of-bottle marketing claims.
How to Read the Label
Sunscreen is regulated as an over-the-counter drug in the United States, so the label follows a standardized format. Active ingredients and their concentrations are listed in a “Drug Facts” panel, separate from the inactive ingredients. The active ingredients tell you what type of sunscreen you’re dealing with: if you see zinc oxide or titanium dioxide, it’s mineral. If you see names like avobenzone, homosalate, or octocrylene, it’s chemical. Many products use a combination of both.
The percentage listed next to each active ingredient matters. Higher concentrations generally provide stronger protection, but they also affect the product’s texture and wearability. A sunscreen with 25% zinc oxide will offer robust protection but may feel thick and leave a noticeable white cast. One with 10% zinc oxide paired with chemical filters can achieve the same SPF with a lighter feel. The SPF number on the front of the bottle reflects the total protection from all active ingredients working together, not any single one in isolation.