The Unequal Efficacy of Vinegar in First Aid Protocols for Pelagia noctiluca (Cnidaria: Scyphozoa) and Carybdea marsupialis (Cnidaria: Cubozoa) Stings

Although the jellyfish species that inhabit the Mediterranean coastal waters are not lethal, their sting can cause severe pain and systemic effects that pose a health risk to humans. Despite the frequent occurrence of jellyfish stings, currently no consensus exists regarding the most appropriate first aid protocol among the scientific community. Over the years, several different rinse solutions have been proposed of which vinegar, or acetic acid, is one of the most noticeable as a rinse solution with efficacy data published. We investigated the effect of vinegar and seawater on the nematocyst discharge process in species representative of the Mediterranean region such as Pelagia noctiluca (Scyphozoa) and Carybdea marsupialis (Cubozoa) by means of: (1) direct observation on the nematocyst discharge by light microscope (Tentacle solution assay) and (2) the quantification of hemolytic area (Tentacle skin blood agarose assay). The nematocyst discharge of both species was not stimulated by seawater, and it was classified as a neutral solution. In P. noctiluca, vinegar produced nematocyst discharge per ser while inhibiting the nematocyst discharge of C. marsupilais. These results suggest that the use of vinegar cannot be universally recommended. While in case of a cubozoan C. marsupialis sting, the inhibitory effect of vinegar makes it the best rinse solution par excellence, in case of a scyphozoan P. noctiluca sting, its application can be counterproductive, worsening the pain and discomfort of the stung area.