There are more than 9,000 kinds of jellyfish and many of them can deliver a painful sting. Jellyfish can make the diver’s life an itchy, painful nightmare — and even kill. Their tentacles contain nematocysts, sacs armed with barbs propelled at the speed of a bullet that inject a venom with both toxic and immune system effects.
Envenomations result in intensely itchy red welts or blotches. While these usually resolve within a week or two, they may linger, and can resolve only to return weeks later. In some cases, blisters develop and areas of skin die and slough off, even leaving long-lasting skin discoloration or scarring. In severe cases, fever, headache, nausea, difficulty in swallowing or breathing, faintness, rapid heartbeat, weakness, and muscle spasms may occur.
Prevention includes passing on scuba during times of heavy infestation or wearing a full- body protective suit that fits snugly at the neck, wrists, and ankles. Safe Sea, applied before getting stung, often substantially reduces both skin reactions and discomfort.
If zapped, here are self-remedies that should be performed as soon as possible:
1. Remove any graspable tentacles with tweezers; then use a razor (carefully) to shave away any remaining particles. A sand-and-seawater paste and a credit card or driver’s license, or even a sharp-edged shell, will work in a pinch.
2. Apply copious amounts of white vinegar to the affected area(s) and repeat this several times during the first 30 minutes after the sting. (Note: Do not use vinegar for a Portuguese man-of-war; it can trigger any remaining nematocysts to fire.)
3. Follow these actions with the topical application of hydrocortisone (prescription strength preferred). You may substitute Benadryl lotion or a calamine preparation with menthol, but these are less effective.
4. Use oral analgesics to control pain.
5. Immerse the affected area in hot water for 30 to 90 minutes to reduce pain. You can also apply warm packs (113F/45 degrees C max) to control the pain. This may be repeated as necessary.
6. Oral antihistamines such as Claritin may also provide relief
Note: Analgesics and antihistamines can cause drowsiness and therefore be unsafe for use while diving.
Myth Buster: While you’ve likely heard that peeing on such stings will help, a number of diving medicine experts think this is an old wives tale, and may in fact cause unreleased nematocysts to fire and result in other problems.
Whatever steps you take, expect to tough it out for a bit, and if you don’t get satisfactory resolution from self-treatment, the reaction is severe, or the eruption gets worse or infected, seek medical attention. And keep in mind that some stings, like those from a box jellyfish, can be very toxic, even fatal. Watch for severe symptoms, like pronounced swelling, trouble breathing, muscle weakness, and nausea, that require immediate attention.
DocVikingo has been scuba certified for more than 35 years and has dived all over the world. He is a practising doctor in the Baltimore/Washington, D.C. area and has held faculty positions at several major hospitals, including Johns Hopkins. With an interest in diving medicine, he serves as administrator at Scuba Clinic Online.