A randomised controlled trial of hot water (45°C) immersion versus ice packs for pain relief in bluebottle stings

Conrad Loten, Barrie Stokes, David Worsley, Jamie E Seymour, Simon Jiang and Geoffrey K Isbister
Med J Aust 2006; 184 (7): 329-333.


Objective: To investigate the effectiveness of hot water immersion for the treatment of Physalia sp. (bluebottle or Portuguese Man-of-War) stings.

Design: Open-label, randomised comparison trial. Primary analysis was by intention to treat, with secondary analysis of nematocyst-confirmed stings. One halfway interim analysis was planned.

Setting: Surf lifesaving first aid facilities at two beaches in eastern Australia from 30 December 2003 to 5 March 2005.

Participants: 96 subjects presenting after swimming in the ocean for treatment of an apparent sting by a bluebottle.

Interventions: Hot water immersion (45°C) of the affected part versus ice pack application.

Main outcome measures: The primary outcome was a clinically important reduction in pain as measured by the visual analogue scale (VAS). Secondary outcomes were the development of regional or radiating pain, frequency of systemic symptoms, and proportion with pruritus or rash on follow-up.

Results: 49 patients received hot water immersion and 47 received ice packs. The two groups had similar baseline features, except patients treated with hot water had more severe initial pain (VAS [mean ± SD]: 54 ± 22 mm versus 42 ± 22 mm). After 10 minutes, 53% of the hot water group reported less pain versus 32% treated with ice (21%; 95% CI, 1%–39%; P = 0.039). After 20 minutes, 87% of the hot water group reported less pain versus 33% treated with ice (54%; 95% CI, 35%–69%; P = 0.002). The trial was stopped after the halfway interim analysis because hot water immersion was shown to be effective (P = 0.002). Hot water was more effective at 20 minutes in nematocyst-confirmed stings (95% versus 29%; P = 0.002). Radiating pain occurred less with hot water (10% versus 30%; P = 0.039). Systemic effects were uncommon in both groups.

Conclusions: Immersion in water at 45°C for 20 minutes is an effective and practical treatment for pain from bluebottle stings.

  • Conrad Loten1
  • Barrie Stokes2
  • David Worsley1
  • Jamie E Seymour3
  • Simon Jiang2
  • Geoffrey K Isbister4,5

  • 1 Hunter New England Area Health Service, Newcastle, NSW.
  • 2 University of Newcastle, Newcastle, NSW.
  • 3 Department of Tropical Biology, James Cook University, Cairns, QLD.
  • 4 Tropical Toxinology Unit, Menzies School of Health Research, Charles Darwin University, Darwin, NT.
  • 5 Department of Clinical Toxicology, Newcastle Mater Hospital, Newcastle, NSW.



We thank all the members of the surf lifesaving clubs and surf lifesavers employed by Newcastle City Council for their assistance in identifying patients for the study. We particularly thank Nobby’s and Dixon Park Surf Lifesaving Clubs for allowing us to use space in their clubs and install the thermostatic mixing valves. We thank Enware Australia for providing cost-price valves and Macs Plumbing for their installation. We thank John Bolton for assistance in obtaining council permission to undertake the study and Kate Armstrong and Paul Healey for recruiting patients. We thank Tony Smith for his comments on the manuscript. The study was partially funded by a Margaret Mitchell Grant (Newcastle Mater Hospital Internal Grant) and a donation from the NSW Surf Life Saving Council. Geoffrey Isbister is supported by a National Health and Medical Research Council Clinical Career Development Award ID300785.

Competing interests:

None identified.

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