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Coral Toxicity

Editor: Vikas Gupta Updated: 8/7/2023 11:59:20 PM


Corals are invertebrates that fall within the class Anthozoa of the phylum Cnidaria. They are mostly marine inhabitants and typically live in compact colonies of numerous polyps. They are one of the important reef builders in tropical oceans. Many corals, like Zoanthid corals, also known as soft corals, are a very popular component of aquariums (home or public) due to their beauty and low maintenance. Species of Zoanthid corals like Palythoa and Zoanthus species can contain a highly toxic and potentially lethal chemical compound known as palytoxin. Coral toxicity, therefore, is palytoxin toxicity. Aquarium shop workers and home aquarium hobbyists may be at increased risk of exposure. So these corals have important implications in human health, but the health risks associated with such corals are often unrecognized or underestimated due to the low volume of cases documented. 

Palytoxin (PTX) is a polyhydroxylated and partially desaturated non-proteinaceous substance that is highly toxic. It is one of the largest naturally occurring polymeric product with a molecular weight of 2680 kilodaltons. Its lethal dose (LD) in mice, when administered intravenously, is 150 ng/kg body weight. PTX has also been found in certain fishes,  phytoplanktons, and in certain marine bacteria. Toxicity from sources other than corals has also been routinely reported.

In recent years the toxicological implications of PTX on human health due to the exposure to soft corals have been on the rise. The number of human poisonings, mostly in aquarium enthusiasts after the manipulation of PTX-contaminated soft corals, is continuously increasing. It is due mainly to the lack of sufficient control over coral trade, and also underestimation and limited understanding about the entity.[1][2]


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PTX exposure, and resulting toxicity via coral, is mostly associated with inhalation of vapors during cleaning, scrubbing, or eradicating the coral from home/public aquariums. Due to the rapid growth of zoanthids, it requires regular removal from specific unwanted areas of the aquarium. The removal process is mostly by boiling in water and/or scrubbing out from rocks. This process may result in inhalation of steam or aerosolized droplets. Also, instances of dermal absorption from prolonged and unprotected handling of PTX containing coral have been reported. It can occur via both intact and broken skin.  

PTX toxicity can occur due to the consumption of seafood capable of producing PTX or seafood contaminated with corals. Also, reports of corneal toxicity have been reported caused by PTX.[1][3][4][5]


Zoanthids are common in oceans of tropics and subtropics; this includes coastlines of Hawaii, Florida, Brazil, Australia, Japan, and many Atlantic islands. They usually live in the shallow, hard-bottom floors of the ocean up to 12 meters deep. However, zoanthids can be easily purchased online so that the toxicity can occur at any place. The majority of the cases of Coral toxicity are among aquarium enthusiasts. In recent times, an increasing number of cases of inhalational exposures have been reported among aquarium handlers during the cleaning or handling of coral for a prolonged time.[6]


Poisonings associated with PTX-contaminated soft corals are mostly through inhalation or dermal absorption. However, the ingestion of corals or surrounding seawater is a less probable, but not impossible event.

The exact in vivo mechanism of the toxicity of PTX is not clearly established. PTX is known to be a potent vasoconstrictor. It's neurotoxic, cardiotoxic, and metabolic effects are mainly due to dysregulation of Na/K ATPase, a transmembrane pump. PTX locks into the pump in α-β ATPase heterodimer leading of sequence of conformational changes and thereby allows passive transport of both ions(sodium and potassium), which in turn destroys the ion gradient which is the very essence of cellular homeostasis. Therefore, PTX can affect any cell line depending upon the mode of exposure.[1][5][7][8][9]

History and Physical

In recent times, there is increasing evidence of inhalational and/or cutaneous exposure to PTX after handling PTX contaminated soft corals. Coral toxicity due to palytoxin depends on the duration of exposure, the route of exposure, and the distance from the location where the coral was being handled. The patient may seek medical attention minutes to hours after the maintenance of home aquaria. A detailed history regarding patient activity before the symptoms and also patient hobbies and occupation would yield useful information.

The patient usually describes an event of handling corals, mostly by pouring boiling water and scrubbing coral out of the rocks. The resultant vapor exposure may present with symptoms. Most common presentations are:

Respiratory system

  • Rhinorrhoea
  • Cough
  • Dyspnea

Musculoskeletal System

  • Weakness
  • Myalgia
  • Muscle cramps
  • Rhabdomyolysis

Nervous System

  • Paresthesia
  • Convulsions
  • Dizziness
  • Numbness
  • Restlessness

Other systemic symptoms

  • Fever
  • Nausea/vomiting
  • Tachycardia
  • Hypotension

Handling of corals with intact or damaged skin for a prolonged period may result in dermal absorption of the toxin and present with:

  • Local (edema, erythema, pruritus)
  • Perioral paresthesia
  • Dysgeusia
  • Other non-specific systemic symptoms.

Instances of ocular contamination result in symptoms of keratoconjunctivitis and are non-specific. It includes severe ocular pain, red eye, decreased visual acuity, photophobia, foreign body sensation, and metallic taste.

The patient may present with severe respiratory distress and cyanosis, which can result in progressive respiratory failure and death.[1][3][4][9][10][11][12][13]


The diagnosis of coral toxicity has no confirmatory study or imaging. It is a clinical diagnosis based mostly on a clear history of preceding exposure to PTX containing coral species and the symptomatology that follows. There is a wide variety of possible presentations; therefore, a strong history and clinical suspicion make the foundation for an accurate diagnosis.

PTX has been successfully isolated by the use of high-performance liquid chromatography in some public health cases. However, there is no qualitative or quantitative test used to access human toxicity, and  PTX is not isolated for diagnosis in patients. Recent reports indicate a negative culture for an infectious cause and a temporal relationship to palytoxin exposure. The evaluation of the patient depends upon the mode of exposure and the clinical presentations. This assessment may include an electrocardiogram and respiratory monitoring.[4][10][12]

Treatment / Management

So far, no antidote has been developed against PTX toxicity. Additionally, there is no defined and harmonized medical protocol for the treatment of PTX associated with corals. In general, the management is mainly symptomatic and focused on reducing or limiting the signs and symptoms of toxicity and limiting further damage. Hence, they are defined case by case. Following dermal and ocular exposure, rinsing the affected area with water is useful to reduce the toxicity.  

Many approaches regarding inhalational exposure of PTX have been under study. One approach focuses on the usage of nebulized β-agonists or corticosteroids and/or systemic corticosteroids. Another approach is based on the association of non-steroidal anti-inflammatory drugs (NSAIDs) and nebulized β-agonists or a combination of corticosteroids and antihistamines. For cutaneous exposure, treatment with supportive intravenous fluids infusion, corticosteroids, and antihistamines is mandatory. For ocular exposure and limited toxicity, artificial tears, steroids drops, and/or antibiotics are common choices. More serious damage to the eye like keratitis and ulcers may require surgical exploration and management, such as amniotic membrane transplantation. 

For patients arriving at the emergency department with dyspnea, cyanosis, and respiratory difficulties, progression to respiratory failure should be anticipated, and intensive care should be made available. Also, the toxic effects of PTX to the heart should receive proper attention, using an electrocardiogram.

Animal studies using vasodilators, papaverine, and isosorbide dinitrate have shown that these can serve as antidotes. But the animal experiments showed benefit only after the injection of these agents directly into the heart immediately after exposure.[14][15][16](B3)

Differential Diagnosis

  • Acute Anemia
  • Acute Gastritis
  • Aspiration Syndromes
  • Congenital anomalies of the lungs
  • Hematologic problems
  • Intestinal Perforation
  • Metabolic problems
  • Portal Hypertension
  • Pulmonary air leaks
  • Renal Artery Aneurysm
  • Small Intestinal Diverticulosis
  • Upper Gastrointestinal Bleeding


Patients with mild exposure and minimal symptoms may just require symptomatic treatments and recover well. In cases of serious presentations, including respiratory failure, cardiotoxicity, keratoconjunctivitis, rhabdomyolysis, and kidney failure, there is a significant increase in morbidity and mortality.[14][15][16]


Coral toxicity due to PTX may have various effects and complications depending upon the mode and duration of exposure. Mild toxicities have local and non-specific systemic symptoms. More severe cases can result in hemolysis, cardiotoxicity and myocardial damage, severe respiratory distress, pulmonary edema, rhabdomyolysis, kidney failure, coma, and death resulting from cardiac or respiratory failure. Also, ocular exposure can be severe enough to result in corneal ulceration and even perforation.[14][15][16]

Deterrence and Patient Education

In recent years, there has been growing evidence of inhalational or cutaneous exposure to PTX toxicity associated with corals. It mostly occurs after the handling of PTX-contaminated soft corals, mainly during the cleaning and maintenance of home/public marine aquaria. The high toxic potential of PTX identified in soft corals, and the uncontrolled trade of these zoanthids has raised a serious concern for human health. In fact, with the growing number of documented cases of these poisonings, it can be considered an emerging sanitary problem.

One way to stay safe while keeping an aquarium with any coral would be to presume palytoxin is present. Thus, take appropriate precautions while handling corals to avoid being exposed. Also, the aquarium owners should be encouraged to minimize handling of coral and to use protective wears, including gloves, masks(with activated charcoal filters), and glasses whenever handling the corals. Avoid rough handling of corals, including excessive rubbing, scrubbing, and boiling, as these can produce aerosols and vapors. There have been proposals that the best approach to maintain these species of zoanthids in a home aquaria is their removal by a trained professional. After removal and disposal, water in the aquarium can be cleared of PTX ( over 99%) with the use of activated carbon treatment.

Public health activists can help by focusing on educating the public about this emerging health problem. Also, legal oversight of the buying and selling of corals, may increase awareness and help decrease future cases.[17][18]

Enhancing Healthcare Team Outcomes

Looking into the available literature, most cases are likely to present to the emergency department from minutes to many days of exposure. Mostly the management is supportive, but the range of patient presentations and complications may require an interplay between different healthcare professionals. The management of coral toxicity is with an interprofessional team consisting of emergency department physicians, internists, a toxicologist, intensivists, surgeons, and nurses. Prompt evaluation is necessary to prevent delays in providing appropriate treatment, which can significantly reduce morbidity and mortality associated with coral toxicity. [Level 5]



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