A Guide to Identifying Fire Coral and Treating Its Stings

Close-Up Of Cone Shells On Fire Coral In Sea
Takahiro Inoue / EyeEm / Getty Images

The fire coral  (Millepora dichotoma) is not a true coral at all, but a colony-forming marine organism related to jelly fish and anemones. It is more properly known as a hydrocoral. Like jelly fish, the sea coral can inflict painful stings. Divers in tropical and subtropical waters should take the effort to learn how to identify this organism and avoid it. 

In the following, learn some of the key characteristic to be on the lookout for. Then, we'll briefly discuss methods for avoiding the fire coral altogether, and how to treat stings if you're unfortunate enough to get one. 

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Brownish-Orange or Brownish Green Color, with White Tips

Fire Coral Vertical
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Fire coral is tricky--it disguises itself in regular coral shapes and is often mistaken for seaweed.  Divers have reported seeing fire coral in blade, branching, box, and even encrusting forms. As fire coral is easily confused with other corals, color is a good way to identify it.

Most fire coral is a brownish-orange or brownish-green. It frequently has white tips, like the fire coral trying to hide next to a sponge in this photo.

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Visible Stingers

Fire Coral Polyps
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Most fire coral has visible stingers. Observant divers who get a close look may notice the coral's transparent, hair-like stingers sticking out from fire coral like tiny cactus spines.

The fact that the stingers are hard to see is one of the reasons fire coral stings are so common. A diver may think he is still a few millimeters away from a fire coral, when in reality he has already brushed against the tiny stingers.

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Avoiding Fire Coral Stings

Fire Coral
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To prevent fire coral stings, divers should stay far enough from the reef to avoid even accidental contact. Many apparently benign reefs conceal fire coral.

However, unexpected events may cause even the most careful diver to inadvertently brush against the reef. Wearing a full wetsuit, or even a thin lycra dive skin, will help protect a diver swimming in an area with fire coral.

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Identifying a Sting

Fire Coral Close Up
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Fire coral cuts appear as rashes or red welts and are extremely painful. Fire coral stings may be difficult to diagnose because they do not begin to burn until 5 to 30 minutes after contact, and the diver may not realize at first he has been stung.

Injuries inflicted by marine life can require a variety of different treatments, depending on severity. When possible, divers should consult a doctor familiar with dive medicine to positively identify an injury as a fire coral sting.

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Treating Fire Coral Injuries

Fire Coral and Christmas Tree Worms
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To treat fire coral stings, experienced divers recommend a variety of remedies, but here is a widely accepted method:

  1. Rinse with seawater. Avoid fresh water because it will increase pain.
  2. Apply topical acetic acid (vinegar) or isopropyl alcohol.
  3. Remove tentacles with tweezers.
  4. Immobilize the extremity. Movement may cause the venom to spread.
  5. Apply hydrocortisone as needed for itching. Discontinue immediately if any signs of infection appear.
  6. If no signs of allergic reaction are present, pain may be relieved with an over-the-counter pain medication, like ribuprofen. 
  7. If the diver developsa  shortness of breath; swelling in the tongue, face or throat; or other signs of an allergic reaction, treat for an allergic reaction and seek immediate medical attention. While rare, severe allergies do happen.