Why your swimsuit might actually be making this specific sting worse.
Most beachgoers attribute any sting in the ocean to “jellyfish.” While it is true that jellyfish and Sea Lice belong to the same biological family, they are very different threats.
The difference isn’t just in their biology—it is in how the sting feels, where it appears on your body, and when the pain actually starts.
In this guide, we will explain the invisible threat of Sea Lice (often called “Seabather’s Eruption”) and how to keep your family itch-free this summer.
What Are “Sea Lice”?
First, let’s clear up a common misconception. The “Sea Lice” that sting humans are not lice at all. They are actually the microscopic larvae (babies) of thimble jellyfish (Linuche unguiculata).
DID YOU KNOW? Sea Lice are often present even when the water looks perfectly clear. Because they are the size of a speck of ground pepper, they are usually invisible to the naked eye.
Where and When Do They Strike?
If you are planning a vacation to the tropics, you need to be aware of the “Sea Lice Season.” They are most commonly found in:
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Florida
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The Caribbean
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The Gulf of Mexico
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Cancun and Eastern Mexico
The Danger Zone: In Florida, locals know that Sea Lice peak between Mother’s Day and Father’s Day (mid-May to mid-June). During these peak times, wind and currents can push the larvae near the shore, affecting as many as one in four swimmers.
The Symptoms: How to Spot the Difference
The easiest way to tell if you have been stung by a regular jellyfish or Sea Lice is by looking at where the red marks are.
1. Regular Jellyfish Stings
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Cause: Contact with long tentacles.
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Sensation: Immediate, sharp, burning pain.
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Location: Usually on exposed skin (arms, legs).
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Swimsuit Impact: Your swimsuit usually protects you from the tentacles.
2. Sea Lice (Seabather’s Eruption)
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Cause: Microscopic larvae getting trapped against the skin.
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Sensation: You might feel a slight tingling in the water, but the real symptoms—intense itching—usually start several hours later.
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Location: Primarily underneath your swimsuit (chest, groin, waistline) or under wetsuit cuffs.
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Swimsuit Impact: Your swimsuit actually increases the stinging.
DID YOU KNOW? Nude swimmers are rarely affected by Sea Lice. This is because the larvae need pressure to fire their stinging cells. Without a swimsuit pressing them against your skin, they often wash away harmlessly.
Why Does It Itch So Much Later?
This delayed reaction is the hallmark of Sea Lice. After you leave the water, the larvae are trapped in the fabric of your swimwear. As the suit dries or presses against your skin, the larvae fire their stinging cells.
The symptoms include:
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Intense itching that can last for days or weeks.
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Bite-like marks, small bumps, or blisters under the swimsuit area.
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In severe cases (about 20% of people), symptoms can include nausea, fatigue, and fever.
The “Fresh Water” Mistake
If you suspect you have been swimming in Sea Lice, do not jump straight into a freshwater shower with your swimsuit on.
Fresh water changes the osmotic pressure on the larvae, causing them to fire their remaining stinging cells all at once. This effectively “marinates” your skin in venom.
The Correct Protocol:
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Remove your swimsuit immediately (before showering if possible).
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Wash the swimsuit thoroughly with detergent and hot water (or machine wash) before wearing it again to kill any trapped larvae.
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Shower after the suit is off.
Prevention: How to Stop the Itch
Because Sea Lice are invisible, avoiding them visually is impossible. However, you can create a barrier.
Safe Sea is the only sun protection product scientifically proven to prevent Sea Lice stings.
How to apply it for Sea Lice: Unlike regular sunscreen, where you might miss a spot under your straps, you must apply a generous amount of Safe Sea underneath your swimsuit (on the chest, groin, and waist) before putting your suit on.
When the larvae are trapped between your suit and your skin, the Safe Sea lotion inhibits their stinging mechanism, preventing the venom release even when pressure is applied.
Bottom line: Regular jellyfish sting exposed skin; Sea Lice sting covered skin. Knowing this difference—and applying Safe Sea under your suit—is the key to a happy beach vacation.
