27 year old woman developed red intensely pruritic papules in the area that was covered by her swim suit, 1 day after swimming in the Bahamian ocean.

What is your diagnosis?

Diagnosis: Sea bather’s Eruption (rash)

The rash is caused by jellyfish larvae ( thimble jellyfish ) that get trapped in and under swimwear and hair in salt water. When they dry or get rubbed they rupture and release the irritant toxins that cause the eruption and pruritus. The degree of itching varies and sometimes requires no medical intervention. The rash can last a couple days up to 2 weeks. In this particular case the pruritus was very intense and she was giving a big presentation in 2 days. I gave her an 8 day course of prednisone, 40 qAM x 4 days and then 20 qAMx 4 days. Additionally I recommended Benadryl spray QID to the affected areas, PRN. I saw her back 2 weeks later and she was extremely grateful indicating that her symptoms had greatly reduced 2 days after initiating my treatment recommendations and disappeared completely by day 6.

Keep in mind that this is completely different from Swimmer’s itch, an eruption seen in lakes and freshwater, described in the 2 ‘Cases of the Month’, here:
What are these bumps that appeared after swimming?
12 year old boy with itchy bumps after swimming at lake cabin.

One pearl (for itching) I discovered recently is that Benadryl spray works well to relieve pruritus from both eczematous and histamine etiologies. I am not sure why, but it does and I have used it with good result in many patients. It is inexpensive and readily available.

For additional information on Sea bather’s Eruption see the links below.
		Seabathers
		Sea Bather’S Rash (Sea Lice)
		Dermnetnz.org Sea-bathers
		Cases of the Month Archives