Jellyfish stings vary greatly in severity. Most often they result in immediate pain and red, irritated marks on the skin. Some jellyfish stings may cause more whole-body (systemic) illness. And in rare cases jellyfish stings are life-threatening.

The skin at the site of the stings may look dusky or bluish purple. Healing may take many weeks. Permanent scars may occur at the site of a sting. Sores usually heal without medical treatment.

Unfortunately, in the real world treating a jellyfish sting by urinating on it may actually cause someone in Monica’s situation even more pain, rather than relief. Urine can actually aggravate the jellyfish’s stingers into releasing more venom. This cure is, indeed, fiction.

Jellyfish stings cause immediate, intense pain and burning that can last for several hours. Raised, red welts develop along the site of the sting, which may look like you have been hit with a whip. The welts may last for 1 to 2 weeks, and itchy skin rashes may appear 1 to 4 weeks after the sting.

Most of the 4000 species of jellyfish cause only pain and discomfort when they sting humans. Only Cubozoans, or box jellyfish, of which some 50 species inhabit tropical and temperate seas around the globe, are fatal.

They are pale blue and transparent in color and get their name from the cube-like shape of their bell.

2 to 5 minutes

The box jellyfish Chironex fleckeri is extremely venomous, and envenoming causes tissue necrosis, extreme pain and death within minutes after severe exposure. Despite rapid and potent venom action, basic mechanistic insight is lacking.

Most jellyfish bioluminescence is used for defense against predators. Jellyfish such as comb jellies produce bright flashes to startle a predator, others such as siphonophores can produce a chain of light or release thousands of glowing particles into the water as a mimic of small plankton to confuse the predator.