Chemical vs. Mineral Sunscreen: What the FDA Says

The most important difference between chemical and mineral sunscreen is not the mechanism, it is what the FDA has confirmed about each category. Of the 16 sunscreen actives reviewed under the FDA's OTC Drug Monograph, only two have been confirmed generally recognized as safe and effective: zinc oxide and titanium dioxide, both mineral. Chemical actives including avobenzone and oxybenzone are not confirmed unsafe, but there is insufficient data for a GRASE designation. Swellies uses zinc oxide as its only active because it is one of the two the FDA has fully reviewed and confirmed.

How the FDA Categorizes Sunscreen Actives

The FDA reviews sunscreen active ingredients under the OTC Drug Monograph system. Under Final Administrative Order OTC000006, sunscreen actives fall into one of three categories.

Category I means the FDA has determined the ingredient is generally recognized as safe and effective. GRASE. Two sunscreen actives hold this designation: zinc oxide and titanium dioxide.

Category II means the ingredient is not GRASE. Two actives fall here, aminobenzoic acid (PABA) and trolamine salicylate, and they are no longer permitted for use.

Category III means the FDA cannot determine GRASE status due to insufficient safety data. This is not a finding of danger. It is a finding that the data needed to make that determination has not been provided. Twelve actives are in Category III. These are the actives in most mainstream chemical sunscreens sold in the United States.

The 12 Actives in Category III

The following actives are in Category III under the FDA monograph. They are still legally permitted for sale in the United States, but the FDA has formally requested additional safety data that has not been submitted.

Oxybenzone, Avobenzone, Octinoxate, Octisalate, Octocrylene, Homosalate, Cinoxate, Dioxybenzone, Ensulizole, Meradimate, Padimate O, Sulisobenzone.

Source: FDA Final Administrative Order OTC000006

Category III does not mean these actives are unsafe. It means the FDA requested data to confirm safety and effectiveness and that data has not arrived. That is a fine distinction, but it is a real one. The FDA has been requesting this data for years.

Which Sunscreen Ingredients Are Under Review?

The FDA has formally requested additional safety data on 12 chemical sunscreen actives. Several of them have documented endocrine-relevant activity in lab settings:

Oxybenzone (Benzophenone-3)

The most studied chemical filter for endocrine activity. Oxybenzone has shown estrogenic and anti-androgenic activity in in vitro studies. It absorbs into the bloodstream. FDA studies published in 2019 found it present in blood after a single day of full-body application, at concentrations exceeding the threshold the FDA uses to waive additional safety studies.

The FDA has not concluded that oxybenzone causes hormonal harm in humans. The concern is that the data to confirm it doesn't isn't available either.

Octinoxate (Octyl Methoxycinnamate)

Another common UVB filter with documented estrogenic activity in in vitro studies. Like oxybenzone, it absorbs systemically. Hawaii banned it from reef-protection sunscreens due to coral toxicity. The FDA's position is the same: not confirmed safe and effective, additional data requested, data not yet received.

Homosalate

A UVB absorber found in many everyday SPF products. The FDA's 2019 absorption study found homosalate in blood at concentrations significantly above the threshold for additional safety review. In vitro data shows weak estrogenic and antiestrogenic activity. Not confirmed safe and effective.

Octisalate (Octyl Salicylate)

A UVB filter typically used to stabilize other actives. Documented systemic absorption. Less studied than oxybenzone for endocrine effects, but included in the FDA's category of actives requiring more data.

What Systemic Absorption Means in Practice

In 2019 and 2020, the FDA published studies showing that six chemical sunscreen actives, oxybenzone, homosalate, octisalate, octocrylene, avobenzone, and octinoxate, are absorbed through the skin into the bloodstream at levels above 0.5 nanograms per milliliter after a single day of use. That 0.5 ng/mL threshold is the FDA's benchmark for requiring additional toxicology testing. The studies were published in JAMA.

The FDA was clear that systemic absorption does not automatically mean harm. But it does trigger the requirement for more safety data. That is the data that has not been provided.

In one of those studies, oxybenzone was detected in blood at levels more than 180 times the 0.5 ng/mL threshold after four days of typical use. The FDA did not call oxybenzone unsafe. It said the data needed to evaluate safety had not been submitted. The industry's response was to push back on the testing requirements, not to submit the data.

Zinc Oxide Is Different

Zinc oxide is Category I. The FDA has looked at the evidence and confirmed it: zinc oxide is generally recognized as safe and effective as a sunscreen active.

Zinc oxide is also non-systemic when used as non-nano particles. It does not absorb through the skin into the bloodstream the way the six chemical actives above do. It works at the skin surface, reflecting and scattering UV radiation without entering the body. The mechanism underneath that is mostly absorption.

The FDA has deemed two sunscreen actives safe and effective. Zinc oxide is one of them. That is not a marketing claim. It is the monograph. That is what is in Swellies.

This Is Not a Scare Story

Worth stating plainly: millions of people have used chemical sunscreens for decades without documented widespread harm. The FDA's Category III designation does not mean those products are dangerous. It means the safety question has not been answered to the FDA's standard.

The more honest framing is this: if you are going to apply something to your skin every day for years, it is reasonable to want more than an unanswered safety question. The FDA agrees. That is why it has been asking for the data since 2019.

Choosing mineral sunscreen is not about fear. It is about preferring an active with a fully resolved safety profile over one that is still in regulatory limbo. That is a reasonable preference based on available information.

The Formulation Trade-Off

Here is where mineral sunscreen has historically lost people. Zinc oxide at meaningful concentrations tends to sit visibly on skin, white cast, greasiness, a texture that makes people skip it. That trade-off was real for a long time.

Better formulation has changed it. Polyhydroxystearic acid is a castor oil-derived dispersant that prevents zinc oxide particles from clumping on the skin surface. Paired with iron oxides that neutralize the residual white tone, it is possible to run zinc oxide at 21% and produce a lightweight, non-greasy finish that wears all day without leaving a visible film. That is what Swellies does.

The skin feel argument for chemical sunscreen is real, but it is not permanent. The formulation caught up.

Frequently Asked Questions

What is the safest sunscreen according to the FDA?

The FDA has confirmed two sunscreen actives as generally recognized as safe and effective: zinc oxide and titanium dioxide. Zinc oxide is the only single active that covers both UVA and UVB alone. Swellies uses zinc oxide at 21% as its only UV filter, no secondary actives, no Category III ingredients.

What is the difference between chemical and mineral sunscreen?

Mineral sunscreens use physical UV filters, zinc oxide and/or titanium dioxide, that sit on skin and reflect UV. Chemical sunscreens use organic compounds that absorb UV and convert it to heat. Both can be effective, but only the mineral actives have received the FDA's GRASE designation. Zinc oxide is one of those two confirmed actives. That is what is in Swellies.

Is mineral sunscreen better than chemical sunscreen?

From a regulatory standpoint, mineral actives have the stronger safety record. The FDA has confirmed two sunscreen actives as safe and effective, zinc oxide and titanium dioxide. Chemical actives are not confirmed unsafe; there is insufficient data for a GRASE determination. Swellies uses zinc oxide as the only active because it is the one the FDA has fully reviewed.

Does mineral sunscreen absorb into the bloodstream?

Non-nano zinc oxide particles do not penetrate the skin barrier in meaningful amounts. Multiple studies confirm zinc oxide stays on the skin surface. This is part of why it received the GRASE designation, the safety data is well-established and long-standing. Swellies uses non-nano zinc oxide specifically because it stays where it is supposed to: on the skin surface.

Is chemical sunscreen bad for you?

The FDA's position is that there is insufficient data, not that chemical sunscreens are harmful. Some actives like oxybenzone have been detected in bloodstream studies above the FDA's threshold for requiring additional toxicology testing. That data has not been submitted. "Not proven unsafe" is different from "confirmed safe." The zinc oxide in Swellies has been confirmed safe and effective.

Which sunscreen is better for sensitive skin?

Mineral sunscreen is generally better tolerated. Zinc oxide has anti-inflammatory properties and is less likely to cause irritation than chemical actives. For reactive skin, mineral is the more predictable choice. Swellies has five ingredients, no fragrance, no preservatives, no silicones, which makes it the short-list option for sensitive skin that wants to know exactly what it is applying.

What does GRASE mean for sunscreen?

GRASE stands for "generally recognized as safe and effective." It's the FDA's designation for ingredients with enough safety and efficacy data, from published studies and expert consensus, to be approved for over-the-counter use without additional testing requirements.

Which sunscreen ingredients are FDA approved as GRASE?

Only two: zinc oxide and titanium dioxide. The FDA has reviewed 16 actives total. The other 14 lack sufficient data to earn the GRASE designation, which is why the FDA requested more safety studies in 2019 and 2021.

Does "not GRASE" mean an ingredient is unsafe?

No. The FDA's position on non-GRASE actives is that there is insufficient data, not that the ingredient is harmful. The correct framing is "insufficient data," not "unsafe." But GRASE means the data exists and has been reviewed. That distinction matters.

Why did it take so long to evaluate sunscreen ingredients?

Many sunscreen actives were grandfathered into the market before the modern OTC Drug Monograph process existed. The FDA has been working through formal safety reviews since the 1970s, and the final monograph rule wasn't fully updated until 2021.

One active, zinc oxide. Five ingredients total. See Swellies →