Vinegar has been shown to inhibit neomatocyst discharge in Chironex fleckeri, the deadly north Australian box-jellyfish, and application of vinegar has become accepted first aid, not only for box-jellyfish stings, but also for stings by other Australian jellyfish. However, in a newly differentiated species of Physalia in Australian waters, which causes severe envenomation, vinegar was found to cause discharge in up to 30% of neomatocysts. In treating these stings, the use of vinegar is not recommended as it may increase envenomation. Stings from the single-tentacled Physalia utriculus (the "bluebottle") are not severe, tentacles with unfired nematocysts rarely adhere to the victim's skin and vinegar dousing is not required. Vinegar treatment is therefore an unnecessary step in the first aid management of any Physalia sting but remains an essential first aid treatment for all cubozoan (box) jellyfish tested to date.