Differing Effects of Vinegar on Pelagia noctiluca (Cnidaria: Scyphozoa) and Carybdea marsupialis (Cnidaria: Cubozoa) Stings—Implications for First Aid Protocols

Abstract

The jellyfish species that inhabit the Mediterranean coastal waters are not lethal, but their stings 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 among the scientific community regarding the most appropriate first-aid protocol. Over the years, several different rinse solutions have been proposed. Vinegar, or acetic acid, is one of the most established of these solutions, with efficacy data published. We investigated the effect of vinegar and seawater on the nematocyst discharge process in two species representative of the Mediterranean region: Pelagia noctiluca (Scyphozoa) and Carybdea marsupialis (Cubozoa), by means of (1) direct observation of nematocyst discharge on light microscopy (tentacle solution assay) and (2) quantification of hemolytic area (tentacle skin blood agarose assay). In both species, nematocyst discharge was not stimulated by seawater, which was classified as a neutral solution. In P. noctiluca, vinegar produced nematocyst discharge per se, but inhibited nematocyst discharge from C. marsupialis. These results suggest that the use of vinegar cannot be universally recommended. Whereas in case of a cubozoan C. marsupialis sting, the inhibitory effect of vinegar makes it the ideal rinse solution, in case of a scyphozoan P. noctiluca sting, vinegar application may be counterproductive, worsening the pain and discomfort of the stung area.

Trial Assay for Safe First-Aid Protocol for the Stinging Sea Anemone <em>Anemonia viridis</em> (Cnidaria: Anthozoa) and a Severe Toxic Reaction

“…Herein, we have demonstrated that vinegar application is strictly contraindicated for A. viridis stings due to its potential as an activating solution (Table 1), producing a worsening of the affected area. This is also the case in other species of scyphozoans and hydrozoans [29,33,36,53], including the most important Mediterranean jellyfish P. noctiluca [29], which is responsible for the majority of jellyfish sting cases seeking assistance from lifeguards in certain Mediterranean beaches [18].…”

“…Updated first-aid protocols based on scientific advances are essential tools to prevent harm. In recent decades there has been a growth in scientific reports warning of the ineffectiveness of vinegar as a rinse solution for the treatment of cnidarian stings [29,33,35,36,53], with the exception of cubozoans where its use is effective [29,33,34]. Immediate A. viridis cnidocyst discharge was observed after vinegar application (Figure 4C), indicating it should not be used as a rinse solution following a snakelocks sea anemone sting.…”

“…The diversity of cnidarian species and the lack of studies providing scientific evidence on the effectiveness of first-aid protocols [29] increase the risk of inadequate treatment of users of marine environments. First-aid protocols are focused on two clear actions [30]: (1) rinsing the affected area with a safe rinse solution to remove remaining tissues (e.g., pieces of tentacles) and/or residual cnidocytes after a sting and (2) reducing pain or symptoms.…”

“…First-aid protocols are focused on two clear actions [30]: (1) rinsing the affected area with a safe rinse solution to remove remaining tissues (e.g., pieces of tentacles) and/or residual cnidocytes after a sting and (2) reducing pain or symptoms. Despite the importance, the scientific community remains in disagreement on which are the best rinse solutions or treatments to provide appropriate care, which is confusing for medical professionals, lifeguards and the general public [7,12,29,[31][32][33]. Seawater, vinegar or acetic acid, freshwater and/or baking soda are commonly used as topical rinsing solutions [7], despite the fact that they are not always the best option depending on the stinging species.…”

“…In recent years, researchers have highlighted the importance of establishing species-specific first-aid protocols to avoid extrapolating results that may lead to bad care practices due to differences in cnidocyst response between classes of the Cnidaria phylum [29,33]. Although the use of vinegar has traditionally been recommended [32,34], its unequal effectiveness between species is increasingly supported by scientific evidence [29,33,35]. While vinegar is an inhibitor of cnidocyst discharge in cubozoans [29,34], its application causes immediate discharge in scyphozoans and hydrozoans [29,33,36].…”