Sea Lice

(Seabather’s Eruption)

Sea Lice: What Surfers Need to Know

If you’ve ever finished a surf session in Bali, Lombok, Hawaii, Florida, or the Caribbean and developed an intensely itchy rash, you’ve probably heard other surfers call it “sea lice.”

In human medicine, sea lice refers to seabather’s eruption—an itchy skin rash caused by microscopic jellyfish or sea anemone larvae becoming trapped beneath swimsuits, rash guards, or wetsuits. These tiny larvae release microscopic stinging cells (nematocysts), resulting in skin irritation and inflammation.

Although the rash is uncomfortable, it is usually self-limited and improves with supportive treatment.

What Causes Sea Lice?

Despite the name, sea lice are not insects or parasites living on your skin.

Instead, they are microscopic larvae from marine animals such as:

  • Thimble jellyfish (Linuche unguiculata)

  • Sea anemone larvae

These larvae can become trapped beneath:

  • Rash guards

  • Swimsuits

  • Board shorts

  • Wetsuits

When exposed to freshwater while still trapped in clothing, additional stinging cells may discharge, worsening symptoms.

Common Symptoms

Symptoms usually begin shortly after leaving the water and may include:

  • Intense itching

  • Small red bumps

  • Burning or prickling sensation

  • Rash beneath swimwear or rash guards

  • Skin irritation that worsens over several hours

Less commonly, individuals—particularly children—may experience:

  • Fever

  • Fatigue

  • Headache

  • Nausea

  • Abdominal discomfort

Most cases improve within 1–2 weeks.

Prevention

While sea lice cannot always be avoided, a few simple measures can significantly reduce your risk.

✔ Remove your swimsuit or rash guard immediately after surfing.

✔ Shower only after removing your swimwear.

✔ Wash your swimsuit before wearing it again.

✔ Avoid surfing during known seasonal outbreaks when possible.

✔ Carry hydrocortisone cream and an antihistamine in your surf first aid kit.

Treatment

Treatment focuses on symptom relief.

Most surfers improve with:

  • Oral antihistamines for itching

  • Topical hydrocortisone cream for inflammation

  • Cool compresses

  • Avoiding scratching to reduce skin damage

Seek medical care immediately if you develop:

  • Difficulty breathing

  • Facial swelling

  • Extensive rash

  • Fever

  • Severe pain

  • Increasing redness, warmth, drainage, or other signs of skin infection

When to Seek Medical Attention

While most cases are mild, you should seek medical evaluation if:

  • Symptoms continue to worsen after several days.

  • The rash becomes increasingly painful rather than itchy.

  • You develop fever or flu-like symptoms.

  • Signs of skin infection develop.

  • Symptoms interfere with sleeping or normal daily activities despite treatment.

From a Surfer + Medical Perspective

From a medical perspective, seabather’s eruption is generally a mild inflammatory skin reaction caused by microscopic jellyfish or sea anemone larvae. Although uncomfortable, most cases resolve with conservative treatment and do not cause long-term health problems.

From a surfer’s perspective, however, sea lice can become a significant nuisance—especially during surf trips where you’re spending several hours in the water each day. Long surf sessions, repeated exposure, and tight-fitting rash guards increase the chance of larvae becoming trapped against the skin. Continued scratching can damage the skin barrier and increase the risk of bacterial infection, particularly in warm, humid climates such as Indonesia.

One of the most common misconceptions is that immediately rinsing off while still wearing your swimsuit or rash guard is the best approach. In reality, freshwater can trigger additional discharge of stinging cells if the larvae remain trapped in the fabric. Removing your swimwear first, showering afterward, and washing your gear before wearing it again are simple steps that may help reduce ongoing irritation.

Whether you’re surfing in Indonesia, Bali, Lombok, the Mentawai Islands, Hawaii, Florida, or the Caribbean, being prepared makes a difference. Packing a waterproof first aid kit with hydrocortisone cream, an oral antihistamine, and basic wound care supplies can help you manage symptoms quickly and get back in the water sooner.

Understanding the marine hazards unique to your destination—and knowing when symptoms require medical attention—is an important part of surf travel preparation.

Key Takeaways

  • Sea lice is the common name for seabather’s eruption.

  • The rash is caused by microscopic jellyfish or sea anemone larvae—not true lice.

  • Symptoms usually include intense itching and a red rash beneath swimwear.

  • Remove your swimsuit before showering and wash it before wearing it again.

  • Carry hydrocortisone cream and antihistamines while traveling.

  • Seek medical care if you develop severe symptoms or signs of infection.

Related Articles:

Explore Jellyfish Stings

References

  1. Tomchik RS, Russell MT, Szmant AM, Black NA. Clinical Perspectives on Seabather’s Eruption.JAMA. 1993.

  2. Freudenthal AR, Joseph PR. Seabather’s Eruption.New England Journal of Medicine. 1993.

  3. Wong DE, Meinking TL, Rosen LB, et al. Seabather’s Eruption: Clinical, Histologic, and Immunologic Features.Journal of the American Academy of Dermatology. 1994.

  4. Kumar S, Hlady WG, Malecki JM. Risk Factors for Seabather’s Eruption.Public Health Reports. 1997.