There has long been a debate whether it's best to treat jellyfish stings with heat or cold, and now a team from the University of Hawaii claims to have found the answer.
After combing through more than 2,000 articles and conducting a systematic review of the evidence for the use of heat or ice in the treatment of cnidarian envenomations, the team concluded that the majority of studies to date support the use of hot-water immersion for pain relief and improved health outcomes.
Immersion in hot water (~45°C or 113°F) is a well documented and commonly recommended therapy for being stung by many marine creatures, including the painful stings from echinoderms and venomous fish. The mechanism of action is not entirely clear, but there is evidence that marine venoms are heat labile, and thus immersion of the sting area in hot water is thought to inactivate key venom components.
Ice no longer recommended
Conversely, it was once thought that immersing envenomed areas in ice water might slow the movement of venom towards the core (heart), and thus might lead to better outcomes in deadly envenomations. However, experimental evidence does not support the use of cryotherapy or cold-water immersion in reducing pathology or improving clinical outcomes, and the practice is no longer recommended.
The preponderance of evidence demonstrates that hot-water immersion is a safe and effective method of reducing pain from cnidarian envenomations, and is also associated with improved clinical outcomes. No studies or cases were found where hot-water immersion led to worsened symptoms or poorer clinical outcomes.
Fears of negative effects of immersing a stung limb in 45°C water for 20 minutes are not supported in the literature. This is not surprising, given that hot-water immersion is considered safe and is recommended for the treatment of stonefish stings and other life-threatening marine envenomations with potential cardiovascular complications.