If you're stung by a jellyfish on holiday, take the following steps.
Quickly rinse your skin with large amounts of clean fresh or sea water, followed by surgical spirit (vodka or other spirits will do) or vinegar. Or you can apply moist sea or beach sand for 20 minutes. Or rub with fresh pawpaw or meat tenderiser.
Remove any bits of tentacle stuck to your skin with tweezers or gloved hands, not your bare fingers.
Cover the affected area with over-the-counter hydrocortisone cream three to four times a day until the redness disappears.
To reduce swelling, take oral antihistamines; to relieve pain, take paracetamol (not aspirin - it promotes bleeding, which is a problem with these stings).
If dizziness, nausea, vomiting or other signs of shock develop, get medical help right away.