Jellyfish sting: what to do and what to avoid
After a jellyfish sting, leave the water, remove any tentacle remains with a rigid object without rubbing, rinse only with seawater and apply indirect cold, avoiding fresh water because it triggers the stinging cells still on the skin.
gelisted editorial team · Updated 15 August 2026
The short version
- Fresh water makes the sting worse by firing undischarged stinging cells.
- Intense pain usually lasts 20 minutes to 2 hours.
- Indirect cold is applied in 10 to 15 minute intervals.
- Breathing difficulty or general symptoms mean calling 112.
Most of the remedies passed around on a beach make the sting worse. The correct sequence has four steps and none of them involves tap water.
What to do
Leave the water calmly. Remove tentacle remains with tweezers or the edge of a rigid card, without using bare fingers and without rubbing. Rinse the area with seawater only. Apply indirect cold, a pack wrapped in cloth, in 10 to 15 minute intervals. Then go to the lifeguard post, which has the right materials and can assess the extent.
| Action | Effect | Do it |
|---|---|---|
| Rinse with seawater | washes off remains | yes |
| Rinse with fresh water | fires stinging cells | no |
| Rub with sand or a towel | discharges more venom | no |
| Indirect cold | reduces pain and swelling | yes |
| Direct heat on the area | can increase pain | avoid |
| Remove remains with tweezers | removes the source | yes |
| Assorted household remedies | unsupported and variable | no |
| Duration of intense pain | 20 minutes to 2 hours |
Why fresh water makes it worse
Tentacles carry cnidocytes, microscopic capsules that fire on contact and on changes in osmotic pressure. Fresh water alters that pressure and causes capsules that had not yet discharged to do so, injecting more venom. For the same reason, rubbing the area with sand or a towel mechanically triggers those that remain and widens the affected surface.
When to seek medical help
Breathing difficulty, swelling of the face or lips, dizziness or general malaise, which suggest a systemic reaction and mean calling 112. Stings covering a large surface, or affecting the face or genitals. Stings in young children. Pain that has not settled after 2 or 3 hours. And signs of infection over the following days: increasing heat, spreading redness or discharge.
The mark can remain visible for 2 to 6 weeks, and protecting it from the sun during that time reduces the residual pigmentation.
Prevention in season
Check the beach status before swimming and respect the flag and the lifeguard notices. Onshore winds and currents concentrate specimens near the shore in episodes lasting 2 to 5 days. In areas with frequent presence, a lycra top removes most of the exposed surface, and swimming on patrolled stretches guarantees immediate assistance if it happens.
Frequently asked
+Can I rinse the sting with fresh water?
No. Fresh water fires stinging cells that have not yet discharged and makes the sting worse.
+How do I remove tentacle remains?
With tweezers or the edge of a rigid card, without bare fingers and without rubbing.
+Cold or heat?
Indirect cold in 10 to 15 minute intervals, with a pack wrapped in cloth.
+When should I call 112?
For breathing difficulty, swelling of the face or lips, dizziness or general malaise.
+How long does the mark last?
Two to six weeks. Protecting it from the sun reduces residual pigmentation.
Sources
- 1Ministerio de Sanidad, Gobierno de España (August 2026)
- 2Govern de les Illes Balears, Govern de les Illes Balears (August 2026)