Learn to identify fire coral and stay well away from it.. It won't touch you, you have to touch it! (same goes for sea urchins!)
The treatment for fire coral stings is fairly straight forward in the acute phase.
The pain and rash is caused in a similar way that a jellyfish will cause the problems too. Lots of stinging nematocysts, full of venom, implant into your skin and pump in the poison.
The can be neutralised by vinegar. If your problem persists where you are still itching like crazy you need to get some steroid cream. At this stage I would also make sure there's some antibiotic in the cream too as there may well be itching if you have been scratching the area.
If you wear a 1 mill body suit it will prevent fire coral stings..
Reef Safe Sunscreen
( Please Note: Nothing works better than UV protecting long sleeve shirts!)
Here's something I bet you didn't know: the active ingredients in some sunscreens stay active when they wash off of your body into the sea. When they land on coral reefs, the sunscreens block the beneficial rays of sun which keep bad bugs on the coral at bay, and encourage viruses which eventually bleach and kill the reef.
Every single sunscreen, even the fancy health food store types, have at least one of the four ingredients which cause the damage. The ingredients are: parabens, cinnamates, benzophenones and camphor derivatives. Here are some of the names you'll see on the bottles: Oxybenzone, benzophenone-3, octyl-methoxycinnamate. But look out for parabens and the camphor derivatives, too.
I always wear a rash guard on top to avoid having to use as much sunscreen AND IT PROTECTS AGAINST FIRE CORAL TOO!
We found some great biodegradable sunscreen at Mexitan.com. Don't forget the UV protective clothing! Surfers have used rash guard shirts for years but it's just recently that the SPF 150+ protection these shirts provide while you're in the water has been discovered by the rest of the non-surfing, beach going population AND it means you'll use less sunscreen!