What Does "Reef Safe" Sunscreen Actually Mean?

It came from a law, not a lab.  Here's the background, what the research shows, and where we land.

Written by Dr. Aimee Paik, MD, board-certified dermatologist and VIZE co-founder

In short

"Reef safe" is a marketing term. There is no regulation behind it, and there's no test a sunscreen has to pass to use it. In practice it means a sunscreen was made without oxybenzone and octinoxate, the two filters Hawaii restricted in 2018. The research behind the octinoxate half of that legislation is thinner than you'd expect for an ingredient ban. And when you look at what's actually harming coral reefs, the answer by a wide margin is warming water.

What "reef safe" means on a label

There's no test a brand can run to find out whether its sunscreen is reef safe, so in practice the term almost always means one thing: the formula has no oxybenzone and no octinoxate, the two UV filters Hawaii restricted. Some brands stretch it further to include octocrylene, or use it as shorthand for mineral-only.

So the question worth asking is why those two filters, and not any of the others in a sunscreen. The answer isn't a scientific threshold. It's a bill.

Where the term came from

In 2018, Hawaii made headlines with Act 104, the first statewide sunscreen law of its kind in the U.S.. Starting January 1, 2021, it became unlawful to sell or distribute sunscreen containing oxybenzone or octinoxate in the state without a prescription. Palau and the US Virgin Islands passed their own versions. Key West passed one too, though Florida overrode it at the state level in 2020, so it never took effect.

So why octinoxate? There is laboratory evidence of harm, but it is limited. A 2008 study found that a combination of several UV filters, including octinoxate, could trigger coral bleaching. It did not isolate the effect of octinoxate on its own. Later studies found bleaching and coral death at very high octinoxate concentrations, while lower concentrations have shown effects on associated reef organisms like seagrass. But there was never a large, octinoxate-specific body of research driving the original legislation.

Worth noting what didn't happen. Australia, home to the most studied reef in the world, has no reef-based restriction on sunscreen ingredients at all.

What the research actually shows

When you look at what's affecting the health of coral reefs, here's what the science shows.

Warming water is THE driver. 

Mass bleaching events on the Great Barrier Reef can be explained and predicted by differences in sea surface temperature, including their severity and distinctive geographic footprints. Even the most strictly protected reefs, including no-entry zones nobody swims in, have bleached severely. Remoteness doesn’t enhance coral reef resilience either. In a different study, remote reefs were not found to be more resilient than reefs close to large human populations.

Ocean concentrations are nowhere near the levels that cause harm. 

Octinoxate can stress coral in laboratory studies, but at concentrations far higher than what is usually found in the ocean. In one study, bleaching and coral death occurred at about 1,000 parts per billion (1,000 µg/L). In the real world, levels are typically much lower. Around Oahu, octinoxate was too low to quantify in seawater and coral tissue, and even in heavily touristed Adriatic waters during peak season, the highest level measured was about 1.5 µg/L. Typical ocean concentrations are therefore thousands to as much as a million times lower than the levels linked to coral bleaching in the lab. Overall, environmental risk assessments suggest octinoxate is most concerning in localized, pollution hotspots and worst-case scenarios, rather than at the levels typically found in the ocean.

Oxybenzone is the one filter with real evidence of harm.

Oxybenzone has a stronger environmental case than octinoxate. Laboratory studies have shown that it can damage and kill coral, and a 2021 systematic review found it was the only sunscreen filter that posed a marine risk even at median environmental concentrations, not just at the single highest readings ever reported. Oxybenzone also concentrates in enclosed, heavily visited water. In Hanauma Bay on Oahu, which sees up to 13,000 visitors a day, oxybenzone stayed in the bay for 14 to 50 hours after each release, and two separate analyses found it was a genuine threat to that specific reef. 

Most measured seawater levels are still well below the doses that cause acute toxicity, but newer research suggests that much lower concentrations may matter when corals are already under heat stress. In one study, a field-relevant level of oxybenzone made heat-related coral damage worse, suggesting its greatest real-world concern may be as an added stressor on reefs already struggling with warming oceans. 

The filters most present in the water aren't the ones Hawaii restricted.

The same Hawaii sampling that couldn’t detect octinoxate in surface seawater or coral tissues did find other filters. Homosalate was the most abundant in the seawater and in coral tissues, with octisalate second. Neither one is on Hawaii's list.

Is Cloudwear reef safe?

As we've shared, reef safe doesn't have an established definition, so we don't use the term.

Can you buy Cloudwear in Hawaii? No. We formulated it with 10.15% zinc oxide and 7.5% octinoxate. Octinoxate is one of the two filters Hawaii restricted, so Cloudwear can't be sold there.

We chose octinoxate because it lets the formula stay light and wearable at the protection level we wanted, and because the exposure research on it, at the concentrations actually measured in the ocean, is reassuring. 

If you're heading somewhere with a ban, or you're going to spend the day snorkeling over a reef, buy a sunscreen that complies with the local rule and make sure it's water resistant!