“Sea ticks” is a common nickname for the tiny jellyfish and sea anemone larvae that get trapped under your swimsuit and sting, causing an intensely itchy rash known as seabather’s eruption. They aren’t ticks at all. Getting rid of them requires a specific sequence: remove your swimwear, rinse with salt water (not fresh), treat the rash, and wash your gear in hot water with detergent.
What “Sea Ticks” Actually Are
The organisms people call sea ticks or sea lice are the larvae of two marine species: thimble jellyfish and a type of sea anemone. These larvae are nearly invisible in the water. They drift into your swimsuit, rash guard, or anywhere fabric presses against skin, then fire their stinging cells when squeezed by pressure or friction. The result is a rash that appears in a “bathing suit distribution,” concentrated under the edges of your swimwear, waistband, and anywhere your gear fits snugly.
The condition is most common between March and August along the southeastern U.S. coast, the Gulf of Mexico, and the Caribbean, with the highest numbers from April through July. In Florida, beaches fly purple flags to warn swimmers when larvae are present, and outbreaks increase where the Gulf Stream passes closest to shore.
What to Do Immediately After Swimming
The single most important step is removing your swimsuit as soon as you leave the water. Larvae trapped in the fabric will keep firing stinging cells every time you move. Once the suit is off, rinse your body with clean salt water. Do not start with fresh water. Fresh water disrupts the chemical balance of the larvae and can trigger a greater release of venom, making the stinging worse. After a salt water rinse, you can safely shower with fresh water.
Some sources recommend applying vinegar with 5% acetic acid to the skin right after swimming to deactivate remaining larvae before they fire. However, the American Red Cross notes that evidence for vinegar’s effectiveness varies across species, and they do not broadly recommend it for jellyfish stings in U.S. coastal waters. If you have vinegar handy and the rash is already developing, it’s unlikely to cause harm, but salt water rinsing is the more reliable first step.
Treating the Rash
Seabather’s eruption typically shows up as clusters of small, red, intensely itchy bumps in the hours after ocean exposure. Some people also develop mild fever, nausea, or fatigue, especially children. The rash itself is treatable at home in most cases.
Over-the-counter hydrocortisone cream (1%) applied to the affected areas helps reduce inflammation. An oral antihistamine can control the itching from the inside, which is especially useful at night when the itch tends to feel worse. Avoid scratching, since broken skin can lead to secondary infection. Cool compresses can also take the edge off.
For most people, the rash clears up within one to two weeks. If you develop a high fever, notice spreading redness or pus at the sting sites, or if symptoms worsen rather than improve after several days, those are signs that something more serious may be going on.
Washing Your Swimwear
Larvae and their stinging cells can survive in fabric even after it dries. Simply rinsing your suit isn’t enough. Machine wash all swimwear with detergent and run it through a hot dryer cycle to destroy any remaining cells. If you had a severe reaction, it’s safer to throw the swimsuit away entirely rather than risk re-exposure the next time you put it on. This applies to rash guards, board shorts, and any other gear you wore in the water.
Preventing Stings Next Time
There is no way to completely avoid larvae in affected waters during peak season, but a few strategies reduce your risk significantly.
- Check for beach warnings. Purple flags and local advisories indicate high larval counts. Avoid swimming on those days.
- Wear less fabric, not more. This sounds counterintuitive, but larvae get trapped under clothing. Tight-fitting rash guards and full wetsuits create more surfaces for larvae to lodge against your skin. If warnings are posted, minimizing fabric coverage or skipping the water is your best bet.
- Try a barrier cream. A product called Safe Sea, designed to mimic the protective mucous coating of clownfish, reduced jellyfish stings by 82% in a controlled field trial. It works by making your skin slippery to tentacles and chemically confusing the larvae so they don’t recognize you as something to sting. It doubles as sunscreen and is applied about 10 minutes before entering the water.
- Strip and rinse right after. Even if you don’t feel stinging yet, remove your suit and rinse with salt water immediately after every swim during larval season. Many stings don’t fire until the suit dries and the fabric tightens against the skin.
If You’re Dealing With Actual Ticks at the Beach
Some people searching for “sea ticks” may be dealing with real ticks picked up in beach dune grass or coastal trails. Lone star ticks, in particular, are common in sandy coastal areas along the eastern U.S. If you find a tick attached to your skin, grasp it with fine-tipped tweezers as close to the skin surface as possible and pull straight upward with steady, even pressure. Don’t twist or jerk, which can snap the mouthparts off and leave them embedded. Clean the bite area with soap and water afterward. A tick bite looks like a single red spot or welt, often with a visible puncture point, which is very different from the scattered rash of seabather’s eruption that clusters under swimwear.