Select your country

Shop online

Orca Community Blog

How to deal with a jellyfish sting


September 3, 2021


While exploring in open water, you may encounter some surprises that you wouldn't commonly anticipate would be part of the adventure. An unexpected current, a change in the direction of the wind and the waves with it, or the presence of marine wildlife such as jellyfish are some factors that you can be confronted with on any day swimming in open water.

Jellyfish are already a common topic of conversation for most swimmers. But what do we really know about them? Do they all sting? How should a sting be treated? This article will attempt to answer these and other common questions that so often come to mind.


Jellyfish are organisms that feed on plankton, so their distribution will generally be dependent on the availability of food. Zooplankton proliferations coincide with incidences of more light; with more light, there is more phytoplankton production and therefore more zooplankton production. That is why jellyfish proliferations also coincide with the seasons with higher light incidence, spring and summer. Although this does not mean that they can't be found at other times of the year.

However, the increase in jellyfish depends on several other factors, even if many of them have yet to be proven.

Climatological: With the increase in solar radiation and the decrease in rainfall, the supply of fresh water travelling through rivers to the mainland decreases, which in turn decreases the barrier of different salinity and density that would keep jellyfish away from the coasts. Differences in salinity negatively affect their buoyancy.
Over-fishing: This not only affects populations of natural predators of jellyfish (turtles, tuna, bonitos...) but it also affects species of fish that compete with jellyfish for food; the more food, the easier proliferation is for jellyfish.
Pollution: In areas of oil spills, a type of oil-degrading bacteria is generated. This in turn causes an increase in a type of zooplankton that is the main food source for jellyfish.


Pelagia Noctiluca “Carnation”
Bell diameter: Up to 20 cm
Color: Pink with brown markings
Prevalence: Very high
Danger: High
Habitat: Warm and temperate waters. Found in the open sea forming large swarms. Very wide distribution. Atlantic and Mediterranean
Active periods: Year-round. Most active in the summer.

Physalia Physalis “Portuguese Man O' War”
Diameter: Bell diameter from 10 to 30 cm. Its tentacles can measure up to 20 m. Found in colonies of unisex individuals.
Color: Blue and purple translucent float
Prevalence: Very low
Danger: Very high
Habitat: Warm waters. It is typical of the Atlantic, but has also been observed in the waters of the Mediterranean.
Active periods: Spring - winter

Rhizostoma pulmo “Barrel Jellyfish”
Diameter: up to 40 cm
Color: Blue and white with violet edges
Prevalence: Very high
Danger: Medium
Habitat: Mediterranean and Atlantic. Open and shallow water, usually on the coast. Can be found in swarms or alone.
Active periods: Summer and autumn. In winter its polyps are in shallow waters.

Chrysaora hysoscella “Compass Jellyfish”
Diameter: up to 30 cm
Color: yellow with brown markings
Prevalence: Low
Danger: Medium
Habitat: Pelagic zone. Common in cold open waters. Common on Mediterranean and Atlantic coasts.
Active periods: Spring.

Aurelia aurita “Moon Jellyfish, Common Jellyfish”
Diameter: up to 25 cm
Color: Transparent with 4 violet horseshoe-shaped gonads
Prevalence: High
Danger: Low
Habitat: Pelagic zone. Temperate and cold waters. Lagoons and coastal areas. They develop best in brackish waters.
Active periods: Spring - summer. Abundant in coastal areas and lagoons such as the Mar Menor, but also in fjords and closed bays with inflow of continental waters. Polyps can be found all year round.

Velella velella “Purple Sail”
Diameter: up to 8 cm
Color: Blue disc-shaped body with a transparent float
Prevalence: High
Danger: Low
Habitat: Atlantic, but has been found in the Mediterranean (in spring). Frequently forms large swarms in the surface pelagic zone.
Active periods: Winter and spring. Jellyfish season in autumn - winter.

Phyllorhiza punctata “White Spotted Jellyfish”
Diameter: up to 30 cm
Color: Brown with white polka dots
Prevalence: Very high
Danger: Low
Habitat: Cold, open waters, Mediterranean and Atlantic.
Active periods: Summer

Cotylorhiza tuberculosis “Mediterranean Jellyfish or Fried Egg Jellyfish”
Diameter: up to 35 cm
Color: Yellow and brown, depending on the amount of symbiotic algae. It has an orange-brown central bulge.
Prevalence: Very high
Danger: Low
Habitat: Pelagic zone, open warm waters and coasts.
Active periods: Most active during summer - autumn. Adult jellyfish disappear during the winter, but the polyps survive until the water temperature rises.


Jellyfish stings trigger a toxic reaction which is usually localized. Not all sting with the same intensity, but they are usually painful and cause skin rashes, although in the most severe cases they can cause necrosis and symptoms such as nausea, vomiting, tachycardia, muscle spasms and even fainting. As we have already indicated, the severity of the bite will depend on the species of jellyfish and of course the allergic reaction of the person.

What should one do in case of a bite? 

Rinse with sea water, never with fresh water as it could trigger another toxic reaction. Physiological saline solution is very good for cleaning these wounds.
Here are some of the steps you should follow if there is no medical care available nearby to treat the sting:
• Remove any remains of tentacles with tweezers and never with bare hands.
• Apply cold compresses that will help with inflammation in the area.
• Apply antiseptic until the wound heals.
• Do not scratch or scrub the affected area.
• Do not dry the skin with a towel.
• Do not apply sand.
• Do not apply ammonia.

Vinegar can be good for most stings, although its use is not recommended if the wound is caused by the following species: Pelagia noctiluca, Chrysaora hysoscella and Physalia physalis.

Once you know the different species that are found in the Mediterranean Sea and the steps to take if you are bitten by one, we hope that you can enjoy your swimming sessions in open water with respect for the marine fauna and flora that make the sea such a special place.