By Ramiro Del Rio

Reef-safe sunscreen for San Blas: what to pack

For San Blas, the sensible choice is a mineral sunscreen with non-nano zinc oxide or titanium dioxide and no oxybenzone or octinoxate. Apply it at least 15 minutes before swimming and cover your back with a long-sleeved rash guard: the less lotion that ends up in the sea, the smaller the chemical load on the reef.

Which filters are under suspicion, and why

The two ingredients that come up most are oxybenzone (also listed as benzophenone-3) and octinoxate (octyl methoxycinnamate).

The study that put the issue on the map was led by Craig Downs and published in 2016 in Archives of Environmental Contamination and Toxicology. The team exposed coral larvae to oxybenzone and found they went from swimming freely to deformed and immobile. They also measured the chemical in the water over reefs in Hawaii and the U.S. Virgin Islands.

NOAA, the U.S. ocean agency, keeps a list of sunscreen chemicals that can harm marine life. Besides those two, it names octocrylene, 4-methylbenzylidene camphor and the nano forms of zinc oxide and titanium dioxide. According to NOAA, coral accumulates these compounds in its tissue, which can lead to bleaching, DNA damage, deformed young and death.

It is worth being precise here: much of the evidence comes from the lab. NOAA itself points to a 2022 report from the U.S. National Academies of Sciences, which found that certain UV filters can harm aquatic life and that a fuller ecological risk assessment is needed. The science is not settled, but choosing the right bottle costs you almost nothing.

Hawaii and Palau have already banned them

Palau was the first country to ban “reef-toxic” sunscreen. The law passed in 2018 and took effect on 1 January 2020; it covers ten substances, oxybenzone and octinoxate among them. The government cited, among other things, a 2017 report by the Coral Reef Research Foundation that found traces of these chemicals in Jellyfish Lake, one of the country’s most visited sites.

Hawaii passed its own law the same year and enforced it from 1 January 2021: since then, over-the-counter sunscreens containing oxybenzone or octinoxate cannot be sold in the state. It was the first U.S. state to do so.

For anyone heading to Guna Yala, the takeaway is practical: a product that would be legal in Palau or Hawaii has already cleared a reasonable bar.

What to look for on the label

Read the active ingredients, not the front of the bottle. “Reef safe” on its own guarantees nothing.

• Mineral filters: zinc oxide or titanium dioxide as the only actives.
• Non-nano: NOAA lists nano particles as a concern, so look for “non-nano” on the pack.
• No oxybenzone, octinoxate, octocrylene or 4-MBC.
• Lotion or stick rather than spray: it goes where you put it, instead of partly into the air and onto the sand.

Less lotion: rash guard, hat and timing

The surest way to keep chemicals out of the sea is to need less sunscreen. NOAA recommends UV-protective (UPF) clothing and staying in the shade between 10 a.m. and 2 p.m.

When you snorkel you spend a long time face down, with your back and the nape of your neck in full sun, which is exactly where people burn. A long-sleeved rash guard solves that without a drop of lotion. On the boat, a hat you can tie down and sunglasses do the rest; the glare off the water burns more than it seems.

If snorkelling is on the plan, read up on what you will see underwater in San Blas and on why starfish should stay in the water.

When to apply it before you swim

The FDA, the U.S. health regulator, advises putting sunscreen on 15 minutes before sun exposure and reapplying at least every two hours, or sooner if you swim or sweat. “Water-resistant” products state on the label whether they last 40 or 80 minutes; none is fully waterproof.

On a day tour that has a simple translation. Pickup is at 05:00 and the 4x4 ride to the port of Cartí takes about 2 h 30, so the best moment to apply it is during the last stretch of road, before you board the boat. Put it on at the water’s edge and jump straight in, and much of it simply floats away.

Why it matters in Guna Yala

The comarca’s reefs are already under pressure, and not because of visitors. The Smithsonian Tropical Research Institute recorded mass bleaching in late 2023 across the archipelago, from El Porvenir to Cayos Limones, linked to warm water during El Niño. The previous mass event on Panama’s Caribbean coast had been reported in 2004.

Sunscreen did not cause that. But travellers cannot control ocean temperature, and they can control what they put in the water. On shallow sandbanks, where many people swim in the same spot at the same time, what each person brings adds up. On a route with several stops, such as island hopping across the cays, you get in and out of the water again and again: one more reason to wear a rash guard and reapply with care.

For a day built around the reef, see Chichime: Snorkeling Among the Reefs or browse all San Blas tours.

Frequently asked questions

What sunscreen should I bring to San Blas? A mineral one, with non-nano zinc oxide or titanium dioxide as the only filters, and no oxybenzone or octinoxate. Lotion or stick works better than spray.

Is it proven that sunscreen harms coral? Lab studies show damage to coral larvae and cells, especially from oxybenzone. A 2022 report by the U.S. National Academies of Sciences found that certain filters can harm aquatic life and called for a fuller risk assessment.

How long before swimming should I put sunscreen on? The FDA recommends 15 minutes before sun exposure and reapplying at least every two hours, or sooner if you swim. On the tour, the best moment is near the end of the 4x4 ride, before boarding the boat at Cartí.

What can I use instead of so much lotion? A long-sleeved rash guard for snorkelling, a hat you can tie down and sunglasses. NOAA also recommends staying in the shade between 10 a.m. and 2 p.m.