Contrary to popular belief, weeing on a jellyfish sting is not the best way to stop the pain.
Scientists say that the best thing to do is wash the area in sea water. Salt water will deactivate the stinging cells - don't use fresh or tap water, as this can reactivate the stinging cells.
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It is also helpful to try to remove the cells carefully with something such as a credit card.
Any remaining tentacles should be removed using tweezers or a clean stick. Applying a heat pack to the affected area, or immersing it in hot water helps to reduce pain and inflammation.
Most jellyfish stings are mild and don't require treatment, or you can treat them yourself - but dial 999 if there are severe symptoms, such as difficulty breathing or chest pain, or if a large or sensitive area of the body such as the face or genitals has been stung.