Can you treat jellyfish stings with vinegar? Spanish scientists explain

AFTER the second-hottest July this century and August lurching from extreme temperatures on one day – around 40ºC in the southern two-thirds of the country – to refreshing thunder storms the next, and September being one of the hottest months of the year, too, heading to the beach is not just indulgence; it's a necessity. 

But one very occasional downside of swimming in the sea is that you may come across the odd jellyfish.

They are not as common as the headlines would make you think – if there are lots of them, lifeguards will 'shut' the sea by hoisting a red flag, as they do when strong currents make bathing unsafe – so the risk of getting stung is actually very low, since you shouldn't be in the water with a red flag flying anyway. 

In fact, you can get fined up to €1,500 if you do, and lifeguards are not obliged to rescue you if you ignore the flag and go swimming; but human nature is that if you've got the skills and you see someone in trouble, you'll dive in without thinking about it, so beach lifeguards will normally put their own safety in jeopardy for you.

This said, jellyfish stings are statistically far more common on Spanish beaches than they are walking down a city-centre street in the UK, so it's good to know what to do if you or someone else suffers from one.

Naturally, urban myths abound – no doubt you've heard about how you should urinate on the sting or squirt vinegar on it – so Spanish scientists have been working on these in order to help us sort the fake news from the genuinely therapeutic.

Depends upon type of jellyfish, and how to tell them apart

The National Research Council-affiliated Sea Sciences Institute in Barcelona (ICM-CSIC) says whether or not the old wives' tales are true depends upon the type of jellyfish: Some, it seems, can be treated with vinegar, but in other cases, it could make them much worse.

Jellyfish stings are not just a painful sensation – they're actually a tangible object and body part, which is left behind in your skin when they've attacked.

And it's crucial to remove all traces of the sting, all cells and tissue residue, from your skin, according to the report in the magazine Toxins.

You probably can't do this yourself, or not entirely, so you'll need someone who's trained – at least a first-aider whose course has included units on jellyfish stings.

Experts recommend rinsing the area with a solution which, in the case of the species known as Pelagia Noctiluca – the one that causes the most incidents on Mediterranean beaches, for example, and which is typically known as the Luminescent or Luminous Jellyfish, or the 'Mauve Stinger' in Australian English – this should never be vinegar.

This is because the stuff you squeeze on your chips or descale your kettle and toilet cistern with actually activates, 'directly and immediately', says the report, the Pelagia Noctiluca's 'stinging cells'; they may lie dormant in your skin after you've been stung and not cause you any pain or irritation, but pour vinegar on it and suddenly, you'll really know about it.

The 'Mauve Stinger' is what it says on the tin: Light purplish in colour, speckled, with long, tape-like tentacles and thin hair-like ones that are harder to spot in passing.

It is mushroom-shaped and, in fact, quite attractive, for a jellyfish, but best avoided – although they will not harm you if you don't go near them.

But vinegar is not contraindicated for every type of jellyfish, says the ICM-CSIC team.

It inhibits the 'stinging cells' from discharging their 'pain juice' into you when you've been attacked by a Carybdea Marsupialis , one of the most aggressive species of jellyfish on the Mediterranean, so vinegar can safely be used to flush out the wound.

This species' common name – Mediterranean Seawasp – says it all, but it is sometimes known as the Box Jellyfish, since it looks like a 'jar' or 'bag' with long, thin tentacles resembling a mouse tail – or an intestinal worm infestation on an X-ray screen - and is clear or white-ish in colour.

“Our findings highlight the importance of recognising the species that has caused the sting and to establish a procedure for the appropriate action in each case,” says researcher and main article author Dr Ainara Ballesteros.

“We have shown that vinegar cannot be used universally, so procedures for the most common Mediterranean species should be based upon scientific evidence to avoid incorrect practices.”

Opposite effects

The researchers analysed the possible effects of vinegar on how a jellyfish sting, once outside its body, discharged its poison cells – known as cnidocytes - examining the two main species along Spain's coasts.

They collected jellyfish from the coast of the province of Barcelona and also the beaches in Dénia, northern Alicante province, where these tend to be more prolific in spring than summer and particularly after a dry winter followed by high temperatures and humidity.

The fact that rinsing with vinegar creates exact opposite effects in the Pelagia Noctiluca and the Carybdea Marsupialis shows there may be huge differences between the species and their subtypes, the team says.

Even though the jellyfish defence mechanism is the same in all types of jellyfish, the level of toxicity and the components in the poison can be very diverse depending upon the 'breed'.

“Our study shows the differences between two disparate cnidarian [cnidocyte-generating] species, but there is still a great deal of work ahead, since it is essential for us to analyse the effects of vinegar in other types which also cause incidents on our beaches,” concludes Dr Josep-Maria Gili of the ICM-CSIC and co-author of the report.

What to do 

As for urinating on jellyfish stings, this has long been ruled out as a solution and, at best, will produce no effect, but could even make the injury worse.

Jellyfish stings off Spanish coasts are rarely dangerous, just painful, and do not normally lead to critical situations, but need to be treated as soon as possible to avoid complications.

If, like most of us, you are unable to tell which type of jellyfish has stung you, and you are on one of Spain's many beaches with lifeguards present – all bar the very remote, rugged ones visited for their natural beauty rather than for sunbathing – the best, safest and most effective solution is simply to go to one of these workers. 

They are first-aid trained, and the service is frequently provided by the Red Cross or a similar organisation, so they will be able to either deal with a sting immediately themselves, or arrange for medical help straight away.