History of Present Illness:
A 25 year-old otherwise healthy male presented to the Emergency Department with a pruritic rash over his abdomen and chest for 2 days. The patient had been swimming and surfing along the South shore of Long Island, NY in August, and noticed an itchy, papular rash develop on his chest and abdomen approximately 2 hours after exiting the water and taking an outdoor freshwater shower. The patient had been wearing a rash guard and riding a boogie board the day the rash developed. He denied any new medications, foods, or prior history of rashes, and did not see any jellyfish in the water.
Past medical, family, social history:
No medications. Non-smoker, occasional alcohol use, no other drug use.
Allergies:
None
Physical Exam:
VS: Normal, AfebrileSkin: Pruritic, pustular papules over the back, chest and abdomen. (see Fig 1)
Discussion:
The differential diagnosis for widespread pruritic papules from an ocean environment encompasses:
Arthropod bite: Usually patient will cite insect bite in the history; Generally arthropod bites are grouped on exposed skin and not as diffuse.
Folliculitis: Usually more pustular and in various stages of healing. If in bathing suit distribution, can be difficult to differentiate from other rashes.
Swimmer’s itch: Pruritic, erythematous papules, often seen in exposed areas not covered by swimwear. The larval schistosomes that cause swimmer’s itch live in fresh or brackish water, so patient usually cites history of swimming in a river, lake, or estuary.
Seaweed dermatitis: Due to fragments of seaweed caught in swimwear. Patient will often cite exposure to seaweed in the history.
Seabather’s eruption (Sea Lice, Sea Ants): Caused by the larval forms of L. unguiculata, also known as the thimble jelly fish, and E. lineata, also known as the lined sea anemone, and other larval cnidaria. The microscopic organisms are trapped under swimwear, and their stingers, called nematocysts, are discharged from the pressure between the skin and swimwear once a surfer exits the water. Free floating larvae suspended in water do not usually sting uncovered skin. The toxins trigger a hypersensitivity reaction, the symptoms of which don’t appear until a couple of hours after the victim has gotten out of the ocean, and lasts days to weeks. The rash is papular, erythematous, distributed under swimwear or hairy parts of the body, and extremely itchy. Due to their minute size, and the fact that symptoms are delayed, surfers are generally unaware that they are sharing the water with a large swarm of stinging larvae.
Based on the history of swimming in the ocean in Long Island, use of a rash guard and boogie board, distribution of the rash, and absence of known arthropod or seaweed exposures, our patient likely had Seabather’s Eruption. A couple of other factors lead to the diagnosis of Seabather’s Eruption. The patient had been swimming in Long Island saltwater, and the single celled larvae of E. Lineata often bloom along the warm waters of the Atlantic seaboard during July and August. In addition, the patient’s symptoms became worse after rinsing in freshwater, and freshwater is known to facilitate the discharge of the nematocysts, exacerbating symptoms.
Treatment:
Treatment for Seabather’s Eruption is supportive. As pruritus is the most frustrating symptom, patients can generally be treated with systemic antihistamines (diphenhydramine), or topical corticosteroids (Hydrocortisone 1% cream). It is important that patients wash their bathing suits in hot water with detergent to remove any surviving nematocysts before using the same swimwear. In order to prevent development of Seabather’s Eruption, counsel your patients to rinse off with saltwater or even remove bathing suits and rash guards before getting out of the ocean (although this might be challenging if you aren’t at a nude beach!).
Case Outcome:
Patient was discharged with prescription for hydrocortisone 1% cream.
Lost to follow up but hopefully still surfing!
Sources:
Prohaska J, Tanner LS. Seabathers Eruption. [Updated 2020 Jan 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482307/
Nathanson, Andrew, et al. Surf Survival: The Surfer’s Health Handbook. 2nded., Skyhorse Publishing, 2019.
Michael S. Tcheyan, MD, Rhode Island Hospital, Providence, Rhode Island
Alyssa R. Mierjeski, MD, Rhode Island Hospital, Providence, Rhode Island.
Email: miketcheyan@gmail.com