Sea lice, a common term for seabather’s eruption, are not parasitic lice but microscopic larval forms of thimble jellyfish and sea anemones. These nearly invisible marine organisms cause an allergic reaction upon skin exposure. Discomfort ranges from mild itching to a widespread rash, requiring treatment and prevention.
Recognizing Sea Lice Bites
A sea lice rash, also called seabather’s eruption, has distinct symptoms. It typically manifests as small, itchy, red bumps, often clustered, resembling acne or hives. Bumps commonly appear on skin covered by swimwear, hair, or wetsuits. Larvae become trapped by fabric, and friction or freshwater triggers stinging cells.
Symptoms usually begin shortly after leaving the water, though a prickling sensation may be felt while swimming. The rash typically develops within 4 to 24 hours after exposure. Intense itching and burning are common. Systemic symptoms, especially in children, can include mild sickness, fever, chills, nausea, vomiting, or headache. The rash generally subsides within a few days to two weeks, but can persist for up to a month.
At-Home Treatment Strategies
Immediate action after potential exposure can help limit the severity of a sea lice rash. It is important to remove wet swimwear as soon as possible, ideally before rinsing with freshwater, as freshwater can trigger the release of stinging toxins from trapped larvae. After removing swimwear, rinsing the body in uncontaminated seawater or showering with fresh water is advisable.
Applying diluted vinegar or rubbing alcohol to the affected skin can help neutralize toxins released by any remaining stinging cells. For soothing discomfort, a cool compress or an ice pack wrapped in a cloth can be applied to the irritated areas. Over-the-counter topical anti-itch creams, such as hydrocortisone (1%) or calamine lotion, can provide relief from itching and inflammation.
Oral antihistamines, like diphenhydramine, fexofenadine, or cetirizine, are effective in reducing the allergic reaction and itching. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen can help manage pain and inflammation. Avoid scratching the rash to prevent secondary skin infections.
Medical Treatment and When to See a Doctor
While most cases of sea lice rash resolve with at-home care, certain symptoms warrant medical attention. Seek medical help if the rash becomes widespread, worsens despite home treatment, or shows signs of infection like increased redness, warmth, swelling, pus drainage, or streaks. Consult a doctor if systemic symptoms like high fever, severe nausea, vomiting, or difficulty breathing occur.
A healthcare provider may prescribe stronger topical corticosteroids if the rash is severe or affects sensitive areas like the face, groin, or armpits. In more severe cases, oral corticosteroids, such as prednisone, may be prescribed to reduce inflammation. If a secondary bacterial infection develops from scratching, antibiotics may be necessary. Children and individuals with allergies or compromised immune systems may experience more severe reactions and should be monitored closely.
Preventive Measures
Preventing sea lice rash involves several practical steps to minimize exposure to the larvae. Check local beach reports and lifeguard warnings for advisories about sea lice or jellyfish larvae. Avoid swimming in areas known for outbreaks, especially during peak seasons (March through August in warm ocean waters), to reduce risk.
Wearing protective swimwear, such as rash guards or full-body stinger suits, can create a physical barrier against the larvae. Tighter-fitting swimwear may be preferable to loose-fitting clothes or t-shirts, which can trap more larvae. Immediately after swimming, remove swimwear and shower.
Wash swimwear thoroughly with hot water and soap after use, as larvae can remain in fabric and cause a recurring rash. Drying swimwear in a dryer, rather than air-drying, helps eliminate larvae. Some protective lotions and barrier creams are available that claim to prevent stings by inactivating stinging cells or creating a slippery surface that prevents larvae from attaching.