Fire corals are colonial marine cnidarians that when touched can cause burning skin reactions. Fire-coral-related incidents are common among divers with poor buoyancy control.

fire-coral-rashBiology and Identification
Fire coral, which belong to the genus Millepora, are found in tropical and subtropical waters around the world. Generally fire coral adopts a yellow-green or brownish branchy formation, although its external appearance often varies due to environmental factors. Because fire coral can colonize hard structures, it can even adopt a rather stony appearance with rusty coloration.

Despite their calcareous structure, fire coral is not a true coral; these animals are more closely related to Portuguese man-of-war and other hydrozoans.

Mechanism of Injury
Fire coral gets its name because of the fiery sensation experienced after coming into contact with a member of the species. The mild to moderate burning that it causes is the result of cnydocites embedded in its calcareous skeleton; these cnydocites contain nematocysts that will fire when touched, injecting their venom.

Signs and Symptoms
The burning sensation may last several hours and is often associated with a skin rash that appears minutes to hours after contact. This skin rash can take several days to resolve. Often, the skin reaction will subside in a day or two, but it may likely reappear several days or weeks after the initial rash disappeared.

Fire-coral lacerations, in which an open wound receives internal envenomation, are the most problematic fire-coral injuries. Venom from Millepora spp. is known to cause tissue necrosis on the edges of a wound. These injuries should be carefully observed, as necrotic tissue provides a perfect environment to culture serious soft tissue infections.


  • Avoid touching these calcareous formations.
  • If you need to kneel on the bottom, look for clear sandy areas.
  • Remember that hard surfaces such as rocks and old conchs may be colonized by fire coral even if they do not look branchy.
  • Always wear full-body wetsuits to provide protection against the effects of contact.
  • Master buoyancy control.
  • Always look down while descending.

First Aid

  1. Rinse the affected area with household vinegar.
  2. Redness and vesicles will likely develop. Do not puncture them; just let them dry out naturally.
  3. Keep the area clean, dry and aerated — time will do the rest.
  4. For open wounds, seek a medical evaluation.NOTE: Fire-coral venom is known to have dermonecrotic effects. Share this information with your physician before any attempts to suture the wound, as the wound edges might become necrotic.
  5. Antibiotics and a tetanus booster may be necessary.