Ahhh, the scourge of the Caribbean Sea! Many of us have experienced this itchy, annoying rash, and most of us know that it has something to do with Thimble Jellyfish, but there is still a lot of speculation on how we get sea itch and how to treat it.
First let’s clear up a few misconceptions. Using the term ‘sea lice’ when describing this condition is inaccurate. Sea lice is a malady that affects fish, not humans.
Another common misconception is that sea itch is caused by the larvae from Thimble Jellies burrowing under the skin and growing – yuk!
Larvae from Thimble Jellies are the culprits that give us sea itch but the dermatitis (rash) is caused by stinging structures called ‘nematocysts’ surrounding the larvae. When we go swimming these larvae, no larger than a pinhead, get trapped between our swimsuits and skin or collect in our hair and body creases.
The nematocysts ‘fire’ when pressure is applied to them or when they are exposed to a foreign environment such as air or fresh water.
Sea itch is a seasonal affliction with outbreaks occurring intermittently between March and August, and peaking between mid-April and early July.
It’s important to remember that although adult Thimble Jellies may be present in the early part of sea itch season they die after spawning so the absence of adult animals does not mean that there are no larvae in the water.
Dermatitis usually becomes noticeable between four and 24 hours after exposure, although some people complain of a prickling sensation while still in the water.
Persons who have had previous exposure to sea itch tend to have immediate stinging sensations on re-exposure.
Local dive professionals claim that covering exposed skin with baby oil or Vaseline will protect against sea itch and that dousing with vinegar immediately after exiting the water will lessen or eliminate the dermatitis by neutralizing the nematocysts.
Generally dermatitis is the only symptom; however in very rare cases (usually with young children) the patient may experience nausea, vomiting, diarrhea, headache, fever, or muscle spasms.
The dermatitis can easily be treated with over the counter medications available from your pharmacist. Apply a Hydrocortisone cream to the rash areas and take an oral antihistamine such as Benadryl to soothe the itching (to avoid possible drug interactions do not use Caladryl lotion or any other topical preparation containing diphenhydramine if taking an oral antihistamine).
In cases where dermatitis covers a large area of the body and significant swelling is present, or if other side effects occur, see a physician.