Jellyfish Sting: Never Rinse in Fresh Water

Key takeaways

The first thing most people do — sluicing fresh water over it to clean it — is the thing that makes the sting worse. According to CDC, rinsing with fresh water may make the stinging cells release more venom. What is needed is sea water, poured on generously.
Do not touch tentacles still stuck to the skin with bare hands. Lift them off with something: CDC names tweezers or the edge of a plastic card, NHS names tweezers or the edge of a bank card.
Do not apply ice. NHS puts ice and cold packs on the list of things not to do for a marine creature's sting — the opposite of a bee sting, so do not carry the bee approach over to this.
Mild pain in the first minutes is not a measure of anything. According to CDC, someone stung by an Irukandji jellyfish may have only mild pain at first, with severe symptoms appearing afterwards.

When a jellyfish stings, almost everyone's reflex is to sluice fresh water over it to clean it — and that is precisely the thing that makes the sting worse. According to CDC, rinsing with fresh water may make the stinging cells release more venom. What is needed is sea water, poured on generously, right there on the spot.

Recognising it: the mark of a jellyfish sting, and what it is confused with

A jellyfish sting usually leaves a streak or a long line following the path the tentacle brushed across the skin — not a single round spot the way a bee sting does.

Burning, stinging pain the moment of contact with the jellyfish; skin red and raised along a long streak
Itching and prickling around the streak, usually worst in the first hours and then easing
Blisters along the streak — MedlinePlus describes intense burning pain with blisters at the site of the sting with box jellyfish
Almost transparent tentacles still stuck to the skin, very hard to see; touching them stings your own fingers
Easily confused with other things in the water: CDC groups sea urchins, jellyfish, coral and sea lice together, so ask local people before going in

Mild pain at first does not mean this is mild

According to CDC, someone stung by an Irukandji jellyfish may have only mild pain at first, with a whole set of severe symptoms arriving afterwards — listed in the red flag box below. CDC notes that this group usually needs emergency treatment in hospital.

What to do now

None of the following needs a prescription. Do them in this order.

Get out of the water and away from where the jellyfish are. A tentacle detached from the jellyfish can still sting.
Pour plenty of sea water over the sting. According to CDC, if tentacles are still stuck to the skin, remove them as soon as possible by pouring sea water on generously.
Lift off remaining tentacles or spines with an implement, not with bare hands: CDC names tweezers or the edge of a plastic card; NHS names tweezers or the edge of a bank card.
Soak the stung area in warm water — NHS says as hot as can be tolerated — for at least 30 minutes; if soaking is not possible, apply a cloth dipped in warm water. Test it on unaffected skin first.
Leave the sting uncovered — NHS says do not cover or close the wound.
Pain relief: NHS names paracetamol (acetaminophen) or ibuprofen for marine creature stings; which one and how much is a decision for a doctor or pharmacist.
Note down the time of the sting and which stretch of coast it happened on, then stay with the person for the hours that follow.

Things you must NOT do

Do not rinse with fresh water, do not sluice tap water or stream water over the sting — according to CDC, fresh water may make the stinging cells release more venom and make the sting worse
Do not rub sand on it, do not scrub with a towel, do not squeeze or press the sting; MedlinePlus says do not rub sand on it, do not apply pressure and do not rub the site
Do not apply ice and do not put a cold pack on it — NHS places this on the list of things not to do for a marine creature's sting, quite unlike a bee sting
Do not urinate on the sting. NHS says this plainly; it neutralises nothing
Do not touch tentacles or spines still stuck on with bare hands, including detached tentacles and a jellyfish washed up on the beach
Do not cover or bandage the sting over
Anyone with a sign in the box below should go to hospital rather than spend longer on first aid

Two points on which the sources disagree

Vinegar: MedlinePlus says to rinse the sting with household vinegar. CDC says vinegar may stop the stinging cells releasing more venom in some Indo-Pacific species, but may INCREASE venom release in temperate-water species. NHS does not mention vinegar. The temperature of the water for soaking is the same story: NHS says as hot as can be tolerated, MedlinePlus gives a specific temperature range. The outcome depends on the species of jellyfish — ask the lifeguards or the medical staff on that beach.

When you must go to hospital

Call 115 (the emergency number in Vietnam) or go to emergency care NOW, without waiting to see whether it settles, if the person stung has any of the following — NHS places these signs in the group that means calling for an ambulance: difficulty breathing; chest pain; seizures; severe swelling around the area stung; heavy bleeding that cannot be stopped; vomiting; feeling faint, collapsing or losing consciousness. Also go to emergency care NOW, even with none of the signs above, if: severe pain spreading beyond the streak, or the appearance of goose pimples, waves of muscle cramp, sweating, a fast heart and a sense of dread as though about to die — according to CDC this is the Irukandji group, which usually needs emergency treatment in hospital; the sting happened on a stretch of coast under a box jellyfish warning — CDC notes this species can cause abnormal heart rhythms and cardiac arrest. BE SEEN WITHIN 24–72 HOURS if: the streak blisters, ulcerates or the skin darkens; the site becomes swollen and hot, with pain increasing, pus, or red streaks spreading out; a fever; itching and a rash around the streak that will not settle; the streak lies over a joint and makes movement difficult; the streak is near the eye.

What belongs at home, and when a medical facility is needed

Most jellyfish stings only hurt and burn locally and can be watched at home, provided fresh water is not poured over them. At home or in a hotel, Y Te Xanh (GreenCare) can do the following: a doctor coming to take a history, examine the sting and say clearly which cases must be admitted; a remote consultation by video call, with a photograph of the sting sent in advance, to decide between going to hospital and watching it; and a nurse examining and assessing a streak that has already blistered or been grazed, changing the dressing and watching for signs of infection.

The signs of anaphylaxis after a sting are described in detail in the bee sting article on this site. With a sign in the box above, go in first and ring afterwards.

According to CDC, jellyfish and related creatures have stinging structures on their tentacles that penetrate the skin and cause pain and irritation; CDC also notes that a marine creature's sting can cause severe pain, needs immediate first aid, and in rare cases is fatal. Citing CDC here does not imply that CDC endorses Y Te Xanh or our services.

Need personalised advice for your loved one? Call our hotline 094 368 81 15 (24/7) — calling to ask a question or to book costs nothing. GreenCare has doctors who come to examine, nurses who carry out doctor's orders (injections, infusions, dressing changes), remote consultation by video call, and a review of the medicines you are taking; an in-depth remote consultation, or any one after the first, is a paid service. For children we take examination and acute care only — not long-term care at home, and not newborns or expectant mothers. We confirm we have staff in your area and provide transparent pricing before we begin.

Sources

MedlinePlus — Jellyfish stings
NHS — Insect bites and stings

Frequently asked questions

Is it harmful to rinse a jellyfish sting with fresh water?

Yes. According to CDC, rinsing with fresh water may make the stinging cells still on the skin release more venom, so the sting burns more rather than less. Pour plenty of sea water on instead. This is the main reason people get worse after coming out of the water: a well-meant effort to clean the wound does the wrong thing.

Should I put ice on a jellyfish sting to ease the burning?

No. NHS places ice and cold packs on the list of things not to do for a marine creature's sting. What NHS does recommend is soaking in warm water, as hot as can be tolerated, for at least 30 minutes. A cold compress is the approach for a bee sting, not for a jellyfish — the two are opposites, so do not apply one to the other.

How long does a jellyfish sting take to heal?

The pain and burning are usually worst in the first hours and then ease, with the red streak fading over a few days. If the streak blisters, ulcerates or the skin darkens, or if the site becomes swollen and hot with increasing pain and pus after a few days, be seen rather than waiting for it to clear on its own. A streak near the eye should also be looked at.

How do I get tentacles off the skin?

Not with bare hands, because touching them stings your own fingers. Pour plenty of sea water on first to wash most of them off — CDC names this as the first way to remove them. Lift the rest off with an implement: CDC names tweezers or the edge of a plastic card, NHS names tweezers or the edge of a bank card. Do it promptly, rather than spending time hunting for some special tool.

Should I put vinegar on a jellyfish sting?

The sources do not agree, so ask the lifeguards or the medical staff on that beach. MedlinePlus says to rinse with household vinegar. CDC says vinegar may stop further venom release in some Indo-Pacific species, but may increase venom release in temperate-water species.

Can a dead jellyfish washed up on the beach still sting?

Do not touch it. NHS says do not touch tentacles or spines with bare hands, and a tentacle detached from the jellyfish can still sting — so both a jellyfish washed up on the sand and the transparent threads lying on it are to be avoided. Children tend to poke them with a stick or pick them up to look, and that is when stings to the hands most often happen.