Seabather’s Eruption

Written by DAN Staff

Part of the job (and sometimes part of the fun) when working with new divers is dispelling myths and misunderstandings about diving and the dive environment. One misunderstanding, and misnomer, you can clear up is about “sea lice,” which should more accurately be called seabather’s eruption. True sea lice are fish parasites and don’t cause the skin irritation that people experience after being in the water.

Seabather’s eruption is caused by the larvae of thimble jellyfish or other tiny planktonic organisms. After encountering these organisms, people experience itchy red bumps that manifest within minutes to hours after swimming, usually in covered areas of the body. Wetsuits are even better than swimsuits at giving larvae and microscopic planktonic organisms an opportunity to hitch a ride. The organisms are small enough to easily entangle themselves in a wetsuit’s lining, especially at the cuffs.

A few things can exacerbate the problem:

•  A wetsuit that’s loose-fitting enough to let water through can act a giant strainer for microorganisms, possibly keeping them in contact with the skin. The friction from a loose wetsuit as it moves around only makes things worse.

•  Peeing in the wetsuit can contribute to making skin more sensitive, and changing the water quality between the suit and skin can excite trapped organisms causing them to sting defensively.

If you find yourself with an eruption and have ruled out other possible causes, there are a few things that may help ease the itchy bumps. The microorganisms that cause this reaction may have nematocysts, which won’t generally release toxins more than once, but they may also have chitinous spikes, which can continue to cause irritation until they’re washed away. A brief soak with vinegar shortly after you notice symptoms may help reduce the irritation. Washing with soap and water followed by a vigorous rinse is also good practice.

Note that some microorganisms that cause this condition can withstand dehydration to become active again when rehydrated. Repeated washing, rinsing and drying will eventually render them inert. The bumps or hives can persist for up to two weeks but will eventually subside. In severe cases, a doctor might prescribe an antihistamine or a steroid.

Washing a wetsuit may not completely disentangle the larvae, and the dehydration of drying does little or nothing to chitin, which means that persistent spikes could cause microscopic skin punctures and a similar rash. So, a few measures can help divers avoid a recurrence:

•  More aggressive means of cleaning, using vinegar or meat tenderizer to soften or dissolve chitin, although it may also affect the glue holding the wetsuit together.

•  Heat and UV light (exposing the suit’s lining to direct sunlight) may help denature the proteins, but again, high temperatures may damage wetsuit materials. Before trying these methods, it’s a good idea for the diver to contact the manufacturer for recommendations based on the suit’s material.

The only practical prevention for seabather’s eruption is avoidance. It’s a good idea to check local reports for notifications or warnings about these organisms being present.

Divers may have heard the term “sea lice,” but knowing a little bit about the actual culprits of this condition will improve their ability to prevent the irritation and effectively clean a wetsuit of microscopic passengers.

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