Palytoxin, PTX[3] or PLTX[4] is an intense vasoconstrictor,[1] and is considered to be one of the most poisonous non-protein substances known, second only to maitotoxin in terms of toxicity in mice.

Exposures have happened in people who have eaten sea animals like fish and crabs, but also in aquarium hobbyists who have handled Palythoa corals incorrectly and in those who have been exposed to certain algal blooms.

[11] According to an ancient Hawaiian legend, on the island of Maui near the harbor of Hana there was a village of fishermen haunted by a curse.

One day, enraged by another loss, the fishermen assaulted a hunchbacked hermit deemed to be the culprit of the town's misery.

While ripping the cloak off the hermit the villagers were shocked because they uncovered rows of sharp and triangular teeth within huge jaws.

The men mercilessly tore the shark god into pieces, burned him and threw the ashes into a tide pool near the harbor of Hana.

[12][13] The moss growing in the cursed tide pool became known as "limu-make-o-Hana" which literally means "seaweed of death from Hana."

[14] It was then assessed by Walsh and Bowers that the limu-make-o-Hana was not a seaweed but a zoanthid coral, subsequently described as Palythoa toxica.

[21] Direct observation of the crystal structure of palytoxin was made in 2022 using microcrystal electron diffraction and an antibody named scFv.

[24] Such fish are scrawled filefish, pinktail triggerfish, Ypsiscarus ovifrons, Decapterus macrosoma (shortfin scad), bluestripe herring and Epinephelus sp.

Bacteria that have some evidence of palytoxin or its analogue production include Pseudomonas, Brevibacterium, Acinetobacter, Bacillus cereus, Vibrio sp.

This was primarily because it was not expected that a pump which provides active transport, could become an ion channel by binding of a compound such as palytoxin.

[28] The breakthrough research which is seen as proof for the sodium–potassium pump mechanism was performed in yeast cells (Saccharomyces cerevisiae).

Values are in micrograms (μg) per kilogram of the animal's weight and have been measured 24 hours after the initial exposure.

[3] An early toxicological characterization classified palytoxin as "relatively non-toxic" after intragastric administration to rats.

[34] As toxin-producing organisms spread to temperate climates and palytoxin-contaminated shellfish were discovered in the Mediterranean Sea[35] a study was done to better define the toxic effects of palytoxin after oral exposure in mice.

One of the possible causes of this behavior is that palytoxin is a very big hydrophilic molecule and therefore the absorption could be less efficient through the gastrointestinal tract than through the peritoneum.

[36] A recent study by Fernandez et al.[37] further investigated on this issue using an in vitro model of intestinal permeability with differentiated monolayers of human colonic Caco-2 cells, confirming that palytoxin was unable to cross the intestinal barrier significantly, despite the damage the toxin exerted on cells and on the integrity of the monolayer.

In this context, despite an increase in reports of palytoxin contaminated seafood in temperate waters (i.e., Mediterranean Sea), there are no validated and accepted protocols for the detection and quantification of this class of biomolecules.

However, in recent years, many methodologies have been described with particular attention on the development of new techniques for the ultrasensitive detection of palytoxin in real matrix such as mussels and microalgae (based on LC-MS-MS[38] or immunoassay[39]).

[2] In some non-lethal cases the symptoms in people have appeared in 6–8 hours after inhalation or skin exposure, and have lasted for 1–2 days.

Other symptoms in humans are bitter/metallic taste, abdominal cramps, nausea, vomiting, diarrhea, mild to acute lethargy, tingling, slow heart rate, kidney failure, impairment of sensation, muscle spasms, tremor myalgia, cyanosis, and respiratory distress.

Other symptoms caused by these aerosols included fever associated with serious respiratory disturbances, such as bronchoconstriction, mild dyspnea, and wheezes, while conjunctivitis was observed in some cases.

[43] People who had eaten smoked mackerel and parrotfish experienced near fatal poisoning in Hawaii[44] and Japan respectively.

[45] There have been palytoxin poisonings through skin absorption e.g. in people who handled corals without gloves in their home aquariums in Germany[46] and the USA.

[47] In 2018, six people from Steventon, Oxfordshire, England were hospitalized after probable exposure by inhalation to "palytoxins" which were released by coral that was being removed from a personal aquarium.

[48] Also in 2018, a woman in Cedar Park, Texas was poisoned when she scraped growing algae from Palythoa polyps in her home aquarium.

The woman described intense flu-like respiratory symptoms and high fever within hours of inhalation and was hospitalized.

[50] A formerly unknown derivative of palytoxin, ovatoxin-a, produced as a marine aerosol by the tropical dinoflagellate Ostreopsis ovata caused hundreds of people in Genoa, Italy, to fall ill.