OBJECTIVES: To determine the benefits and harms associated with the use of any intervention, in both adults and children, for the treatment of jellyfish stings, as assessed by randomised and quasi-randomised trials.

SEARCH METHODS: We searched CENTRAL, MEDLINE, Embase, and Web of Science up to 27 October 2022. We searched clinical trials registers and the grey literature, and conducted forward-citation searching of relevant articles.  SELECTION CRITERIA: We included randomised controlled trials (RCTs) and quasi-RCTs of any intervention given to treat stings from any species of jellyfish stings. Interventions were compared to another active intervention, placebo, or no treatment. If co-interventions were used, we included the study only if the co-intervention was used in each group.  DATA COLLECTION AND ANALYSIS: We used standard methodological procedures expected by Cochrane.  MAIN RESULTS: We included nine studies (six RCTs and three quasi-RCTs) involving a total of 574 participants. We found one ongoing study. Participants were either stung accidentally, or were healthy volunteers exposed to stings in a laboratory setting. Type of jellyfish could not be confirmed in beach settings and was determined by investigators using participant and local information. We categorised interventions into comparison groups: hot versus cold applications; topical applications. A third comparison of parenteral administration included no relevant outcome data: a single study (39 participants) evaluated intravenous magnesium sulfate after stings from jellyfish that cause Irukandji syndrome (Carukia). No studies assessed a fourth comparison group of pressure immobilisation bandages.  We downgraded the certainty of the evidence due to very serious risk of bias, serious and very serious imprecision, and serious inconsistency in some results.  Application of heat versus application of cold Four studies involved accidental stings treated on the beach or in hospital. Jellyfish were described as bluebottles (Physalia; location: Australia), and box jellyfish that do not cause Irukandji syndrome (Hawaiian box jellyfish (Carybdea alata) and major box jellyfish (Chironex fleckeri, location: Australia)). Treatments were applied with hot packs or hot water (showers, baths, buckets, or hoses), or ice packs or cold packs.  The evidence for all outcomes was of very low certainty, thus we are unsure whether heat compared to cold leads to at least a clinically significant reduction in pain within six hours of stings from Physalia (risk ratio (RR) 2.25, 95% confidence interval (CI) 1.42 to 3.56; 2 studies, 142 participants) or Carybdea alata and Chironex fleckeri (RR 1.66, 95% CI 0.56 to 4.94; 2 studies, 71 participants). We are unsure whether there is a difference in adverse events due to treatment (RR 0.50, 95% CI 0.05 to 5.19; 2 studies, 142 participants); these were minor adverse events reported for Physalia stings. We are also unsure whether either treatment leads to a clinically significant reduction in pain in the first hour (Physalia: RR 2.66, 95% CI 1.71 to 4.15; 1 study, 88 participants; Carybdea alata and Chironex fleckeri: RR 1.16, 95% CI 0.71 to 1.89; 1 study, 42 participants) or cessation of pain at the end of treatment (Physalia: RR 1.63, 95% CI 0.81 to 3.27; 1 study, 54 participants; Carybdea alata and Chironex fleckeri: RR 3.54, 95% CI 0.82 to 15.31; 1 study, 29 participants). Evidence for retreatment with the same intervention was only available for Physalia, with similar uncertain findings (RR 0.19, 95% CI 0.01 to 3.90; 1 study, 96 participants), as was the case for retreatment with the alternative hot or cold application after Physalia (RR 1.00, 95% CI 0.55 to 1.82; 1 study, 54 participants) and Chironex fleckeri stings (RR 0.48, 95% CI 0.02 to 11.17; 1 study, 42 participants). Evidence for dermatological signs (itchiness or rash) was available only at 24 hours for Physalia stings (RR 1.02, 95% CI 0.63 to 1.65; 2 studies, 98 participants).  Topical applications One study (62 participants) included accidental stings from Hawaiian box jellyfish (Carybdea alata) treated on the beach with fresh water, seawater, Sting Aid (a commercial product), or Adolph's (papain) meat tenderiser. In another study, healthy volunteers (97 participants) were stung with an Indonesian sea nettle (Chrysaora chinensis from Malaysia) in a laboratory setting and treated with isopropyl alcohol, ammonia, heated water, acetic acid, or sodium bicarbonate. Two other eligible studies (Carybdea alata and Physalia stings) did not measure the outcomes of this review.  The evidence for all outcomes was of very low certainty, thus we could not be certain whether or not topical applications provided at least a clinically significant reduction in pain (1 study, 62 participants with Carybdea alata stings, reported only as cessation of pain). For adverse events due to treatment, one study (Chrysaora chinensis stings) withdrew ammonia as a treatment following a first-degree burn in one participant. No studies evaluated clinically significant reduction in pain, retreatment with the same or the alternative treatment, or dermatological signs.