Jellyfish stings, sea urchin spines and coral cuts on the Vietnamese coast

Most marine injuries along this coast are painful rather than serious, and most are mishandled in the first few minutes by someone trying hard to help. The folk remedies are well known, widely repeated, and several of them actively increase the amount of venom released.

A small set of encounters is genuinely dangerous. They are worth being able to recognise. This page is not a diagnosis of what stung you — identification in the water is unreliable — but the treatment depends less on the species than people assume.

Call 115 for these, from the beach

A sting that causes a reaction away from the skin it touched is an emergency. Get the person out of the water first so that they cannot drown, then call 115 or go directly to the nearest hospital:

• Tightness in the throat, a swelling tongue or lips, wheeze, or any difficulty getting air in
• Faintness, collapse, or skin that has gone cold, clammy and grey
• Chest pain, an irregular or pounding heartbeat, or cramping that spreads across the whole body
• Severe pain that keeps escalating out of proportion to a small mark, which is the stonefish pattern
• A sting across a large area of the body, or any sting with multiple long tentacle welts in a child
• Vomiting, muscle spasm or agitation following a sting rather than during it
• Loss of consciousness in the water, for any reason at all

Anyone who has had a severe reaction before and carries an adrenaline auto-injector should use it early rather than waiting to see, and still go to hospital afterwards. Delayed second reactions are the reason for the second part of that sentence.

What actually stings along this coast

Several things, and the season matters more than the location. Stings cluster in the warm months and after onshore winds, which push drifting animals into the shallows in numbers — a beach that was clear all week can be unswimmable for two days.

Two encounters are common. The small translucent jellyfish that produce a line of nettle-like welts, and the Portuguese man o' war — blue, with a float like a bubble and a very long trailing tentacle that stings badly. Box jellyfish are present in Indo-Pacific waters and are the reason severe reactions are taken seriously, although encounters are uncommon. Sea urchins sit in rock pools and on reef edges. Stonefish bury themselves in sand and rubble in the shallows, which is why footwear matters more than vigilance. Fire coral and barnacles cut rather than sting, and those cuts behave badly in warm water.

Local lifeguards and beach staff know what has been washing in that week. Asking them beats any forecast.

A jellyfish sting, in order

• Get out of the water, and sit the person down somewhere they cannot fall
• Rinse the area with seawater, not fresh water. A great deal of seawater, poured rather than splashed
• Lift tentacles off with tweezers, a stick or a gloved hand. Do not use bare fingers, and do not rub
• Soak the area in hot water. As hot as the skin tolerates without scalding, around forty-five degrees Celsius, for twenty to forty-five minutes. Heat breaks down the venom proteins and it is the measure that most reliably reduces the pain
• If hot water is not available, a cold pack wrapped in cloth will dull the pain, although it does nothing to the venom itself
• Watch the person for an hour even if the pain settles. The reactions that matter develop rather than appear

Vinegar deserves its own note because the advice has changed and both versions are still circulating. For box jellyfish it is recommended, because it stops undischarged stinging cells from firing. For several other species it may make things worse. In practice, if a beach has vinegar bottles on the lifeguard stand it is because the local species warrant it. If not, hot water immersion is the measure.

Four things that make a sting worse

• Fresh water, including a cold shower and bottled drinking water. The change in salt concentration makes intact stinging cells discharge, so a shower can convert a mild sting into a severe one
• Urine. It is not sterile, it is not vinegar, and the dilution effect is the same as fresh water. This is the most widely believed piece of wrong advice on any beach
• Rubbing with sand or a towel, which mechanically fires every stinging cell still sitting on the skin
• Alcohol, spirits or aftershave poured on, which has the same effect for the same reason

If someone has already done one of these before you arrived, the sting will hurt more and look angrier than it otherwise would. Carry on with the hot water anyway; it still helps.

Sea urchin spines

Standing on an urchin leaves spines in the foot. Brittle, barbed, and often deeper than they look. The immediate treatment is the same hot water immersion, which eases the pain considerably.

Remove spines that protrude enough to grip, with tweezers, pulling along the line they went in. Some spines need a clinician. Those snapped off level with the skin, or anything in a joint, over a tendon or in the sole where weight will press on it, should be taken out properly rather than excavated on a beach. Vinegar can soften superficial fragments over a few days of soaking.

What makes urchin injuries matter is not the venom but what is left behind. A retained fragment causes a slow, grumbling infection or a hard nodule weeks later, and the sea urchin that seemed trivial becomes a foot that will not settle. If the pain is still there after several days, something is still in there.

Coral and barnacle cuts heal badly

A coral graze looks like nothing. A few scratches across a shin from a reef, or a hand that brushed a boat hull. Then it does not heal, and a week later there is a raised, inflamed line that stays wet.

Two reasons. Coral leaves calcified fragments and living tissue in the wound, which the body reacts to, and warm tropical seawater carries bacteria that wound surfaces here deal with poorly. These are the cuts that most often need antibiotics out of all the injuries on this page.

So treat a coral cut as a contaminated wound rather than a scratch. Scrub it properly with clean water. Get the fragments out, cover it, and stay out of the sea until it has closed. The last part is the part nobody does. It is the reason the cut is still open at the end of the holiday.

Stepping on a stonefish

This is the injury worth knowing about, even though it is uncommon. The response to it is different. A stonefish is invisible against sand and rubble and injects venom through spines on its back when stepped on. The pain is immediate and extreme. It climbs for an hour or two, far out of proportion to the puncture marks.

Hot water immersion helps, and is worth starting at once. But this one goes to hospital regardless of how the pain is behaving. It can cause swelling that compromises the limb. And an antivenom exists — the decision about it is not one to make on a beach.

Prevention is simple and widely ignored. Wear something on your feet when wading over sand, rubble or reef, and shuffle rather than step.

Past the first day

• Welts and itching from a jellyfish often come back several days later as a delayed skin reaction. It is unpleasant and not an infection
• Increasing pain, spreading redness, discharge or a fever means the wound has become infected and needs assessing
• A puncture — urchin, stonefish, barnacle — raises the tetanus question, and marine punctures count as dirty wounds
• Keep healing marine wounds out of the sea and out of pools until the surface has closed over
• Protect the area from the sun for several months. Marine stings scar with dark pigment surprisingly readily
• A lump that persists where a spine went in is usually a retained fragment, and it needs looking at rather than waiting out

What a clinician does with it

For a straightforward sting, usually very little beyond pain relief and a plan — which is worth saying, because people expect an intervention. The value is in the assessment. Whether this is a local reaction or the beginning of a systemic one, whether anything is retained, whether the wound is contaminated.

Where there is more to do, it is specific. Removing spines or coral fragments under local anaesthetic, cleaning a puncture properly, tetanus cover, antibiotics for a marine wound that warrants them rather than as a routine, and a referral where a limb or a reaction needs hospital care. For a sting that has been treated with urine and a cold shower before anyone arrived, mostly it is the hot water and an honest explanation.

The short version

Seawater to rinse, tweezers to lift, hot water to soak, and nothing fresh, alcoholic or home-made anywhere near it. Get spines and coral fragments out properly. Stay out of the sea while anything is still open. And a sting with breathing trouble, collapse or whole-body symptoms is 115 or the nearest hospital, immediately.