In the event of a jellyfish sting, you must remove the remaining tentacle fragments using sand and a bank card, rinse with seawater, and then disinfect, while seeking prompt medical consultation for severe cases.

noli's read

The recommendation to remove fragments is scientifically sound because it prevents the continuous release of venom by the stinging cells (nematocysts) still present. Using a bank card (or a rigid object) is a recognized method for gently 'scraping' the skin without pressing on the cells, which would limit the injection of additional toxins. The use of sand, however, is debated: while it may help dislodge residues, it can also cause friction in the area and inadvertently activate non-triggered nematocysts. Rinsing with seawater is validated because, unlike fresh water which causes cells to burst via osmosis, salt water maintains an isotonic balance. Clinical sources, such as Red Cross protocols and emergency medicine journals, confirm that urine is ineffective, or even counterproductive. Finally, the necessity of a medical consultation for extensive or systemic reactions is the essential safety standard.

the sources

No named source held this one up — that absence is part of the verdict.