Coral Scrapes and Cuts

Cuts and scrapes are the most common injuries incurred by divers and snorkelers. DAN receives about one inquiry a week related to someone who has come into contact with coral. A burning sensation, pain and itching are common and may also be accompanied by a rash. These injuries can have a latent evolution and take weeks or months to heal, confusing both patients and clinicians.

Mechanisms of Injury

Soft living tissues cover the surface of corals. In the case of stony corals, the rigid (abrasive) structure underneath makes the coral’s soft tissue easy to tear and get into the scrape or cut. Foreign material can prolong the wound-healing process since the different antigens and substances cause an acute inflammatory process and infection. Cuts and scrapes from sharp-edged coral and barnacles tend to fester and may take weeks or even months to heal. Granulomas can form if debris from the original wound remains in the tissue. The body attempts to remove it, resulting in an itchy rash or papule (small, raised, tender bump) that lasts for some time before the body eliminates it.

While most “raspberries” generally heal quickly, skin abrasions from a marine environment can sometimes be more challenging to treat than those we get from outdoor activities such as baseball or bicycling. Whether it is a coral, a rock or a wreck, they all share a common factor: They are covered by living marine organisms, which makes coral cuts and scrapes unique.


The extent of the reaction depends on the presence and amount of toxins, the size and location of the abrasion and the pre-existing sensitivity of the injured person. The most common manifestations are a burning sensation, pain and itching. A rash may accompany the injury if the coral is a hydroid, such as fire coral.

Most animals of class Hydrozoa become hydroids as a life stage. They are predominantly colonial, and while most of them are marine creatures, you can find a few species in freshwater environments.

Fire corals are cnidarians, so they contain nematocysts. Touching them with a simple rub can cause mechanical activation and envenomation. The manifestation is usually blistering, which typically appears a few hours after contact. They typically resolve in a few days, but it is quite common for these injuries to relapse within a week or two after what seemed to be healing progress. This delayed reaction is typical of these types of envenomations.


When underwater, try to avoid contact with coral or any other living creature. Whenever possible, wear a wetsuit or dive skin to protect yourself if you are accidentally pushed into coral by another diver or a current. Ocean divers should consider a marine animal first aid kit for their travels. Ready supplies will speed up the time to properly administer first aid for injuries. Additionally, for divers who want to learn more about the various marine life injuries, there are courses in marine life identification, first aid courses and a variety of books and publications available.

First Aid

  • Scrub the cut vigorously with soap and water, and then flush the wound with large amounts of water.
  • Flush the wound with a half-strength solution of hydrogen peroxide in water. Rinse again with water.
  • Apply a thin layer of antiseptic ointment, and cover the wound with a dry, sterile and non-adherent dressing. If you have no ointment or dressing, you can leave the wound open.
  • Clean and re-dress the wound twice a day.
  • If the wound develops a crust, use wet-to-dry dressing changes. Put a dry sterile gauze pad over the wound and soak it with saline or a diluted antiseptic solution (such as 1% to 5% povidone-iodine in disinfected water). Allow it to dry then rip the bandage off the wound. The dead and dying tissue should adhere to the gauze and lift free. The tissue underneath should be pink and may bleed slightly but should be healing. Change the dressings once or twice a day. Use wet-to-dry dressings for a few days or until they become non-adherent. Then resume the regular wound dressing described above.
  • Look for any signs of infection: extreme redness, red streaks on the extremity, pain, fever, pus or swollen lymph glands. If you have any, consult a qualified health professional about starting an antibiotic. A possible Vibrio bacteria infection can cause illness and even death in someone with an impaired immune system (e.g., from AIDS, diabetes or chronic liver disease).
  • Watch for coral poisoning, which can occur if abrasions or cuts are extensive or from a particularly toxic species. Symptoms include a wound that heals poorly or continues to drain pus, swelling around the cut, swollen lymph glands, fever, chills and fatigue. If you have these symptoms, see a physician.


The most frequent complications from non-stinging coral scrapes are inflammation (which leads to poor healing) and less commonly a secondary infection. Proper wound cleaning is crucial. If fire coral is the culprit, then a diluted acetic acid solution, such as household white vinegar, is a reasonable topical decontaminant and should be used as a soak to reduce the pain. Immersion in hot water can reduce the symptoms. Hot water is ideal, but you can use instant hot packs, cold packs or ice packs. Provide symptomatic treatment for the inflammatory response. Steroid creams are rarely helpful, and they can prolong a skin infection. If the inflammation is severe, you may administer systemic steroids in a moderate, tapering dose under the supervision of a trained medical provider. Oral antihistamines can sometimes help reduce the itching or burning sensation. 

Possible Complications of an Old Problematic Wound

It is not uncommon for divers to contact DAN concerned about a minor skin abrasion on their hands, knees or elbows that happened months ago and has not healed despite proper care. These chronic wounds often have a red and bumpy appearance, occasionally develop a crust and are usually painless. If common antibiotic ointments do not help, divers wonder if the cause may be a marine-specific pathogen.

Divers with an open wound, even a small cut or scrape, are at risk for skin infections. When an old problematic wound fits the descriptions above, it might have become infected with an opportunistic pathogen known as Mycobacterium marinum. Despite the name there are no marine-specific pathogens that affect humans. Some infections are more common in aquatic environments. M. marinum is responsible for a condition commonly known as fish tank granuloma, or aquarium granuloma.

The red and bumpy nodules, no larger than a centimeter, are granulomas — inflammatory immune cells trying to wall off the pathogen. Granulomas are usually isolated but can sometimes appear in small clusters. They are not necessarily painful. There may or may not be discharge from the wound.

Characteristics of M. marinum That Affect Healing

  • The pathogen is opportunistic. It causes infection only in the right conditions (environmental and patient-related), so it is often not considered as a potential culprit.
  • It likes cooler temperatures, which is why these wounds tend to flourish in areas with lower body temperatures such as hands, knuckles, elbows and knees.
  • Only specific antibiotics work, so the typical antibiotic treatments are usually unsuccessful.
  • The life cycle is slow, which means treatments last a long time. Sometimes patients will abandon what could have been a successful treatment or doctors may look for other potential explanations for the symptoms.
  • It requires specific culture media that a doctor would not ask for unless they suspected this pathogen. Standard culture results are often negative, which delays the diagnosis.

Allow your doctor to examine the wound and follow their standard procedures. The doctor will probably ask you how it happened or when it started. Tell them about the superficial abrasion in a marine environment. You may want to ask specifically if M. marinum could be the cause. Your doctor does not need dive-specific medical knowledge for this type of issue.

Fitness to Dive

Always take care of wounds and clean them thoroughly no matter the severity. The skin is our most effective and efficient means of immunological defense. A compromised wound can get seriously infected.

As a rule, treat wounds properly and let them heal before diving. This is particularly important before traveling to a remote location or one with limited local medical care capabilities. A skin lesion with the potential for infection might warrant a more conservative decision to stay ashore if you have such a trip planned.

Chronic skin lesions require specific consultation with your physician team before diving. Your doctor may prescribe treatment or a protective covering to prevent skin breakdown.