The most common envenomations encountered in aquatic environments by humans are by members of the phylum Cnidaria. This phylum includes jellyfish, Portuguese man-of-war, sea anemones, and corals. The common element to all of these groups is the presence of nematocysts or stinging capsules that contain various toxins. Injuries caused by these organisms range from mild irritations to painful, serious injuries with tissue necrosis—sometimes fatal.
Jellyfish and Portuguese man-of-war (Physalia physalis) injuries initially present with sharp burning pain followed rapidly by development of erythematous welts in whip-like patterns on the body. These subside within hours, but resolve to hyperpigmentation in minor cases or bullae and necrosis in severe cases. Systemic symptoms may accompany severe P. physalis injuries and include nausea, abdominal cramps, irritability, chest tightness, and dyspnea.
Stings by Chironex fleckeri, known as box jellyfish or sea wasp (an enormous jellyfish found in tropical Australian waters), are typically severe. The lesions have a characteristic frosted appearance to them due to a dermatonecrotic toxin. Commonly, exposure is fatal due to hemolytic and cardiotoxic toxins. See also Hawaiian box jellyfish sting and lion's mane jellyfish sting.
Sea anemone dermatitis is caused by exposure to one of several species and usually results in conditions similar to allergic contact dermatitis, but differs in that the symptoms occur within minutes of contact.
Exposures to coral may be quite mild and result only in irritation and pruritus. Stings from fire corals, which are not true corals, are painful initially and result in papular and pustular eruptions that can progress to tissue necrosis.
ICD10CM: T63.621A – Toxic effect of contact with other jellyfish, accidental, initial encounter
Jellyfish are aquatic invertebrates that can sting people who come into direct contact with them. The stingers, which are typically located on the ends of the jellyfish tentacles, contain poisons that are often toxic to humans.
Although most jellyfish are not especially dangerous to people, some are extremely toxic.
Portuguese man-of-war is not actually a jellyfish but rather a colony of small, predatory animals (hydrozoan). However, due to their similarity with jellyfish, this information applies to Portuguese man-of-war stings as well.
Who’s At Risk
Stings from jellyfish most often occur in salt water, while swimming or wading, when a person accidentally comes into contact with the jellyfish. Stings from some jellyfish may also occur if a person comes into contact with jellyfish that have washed onto the beach or detached tentacles in the water. Certain jellyfish tentacles that have become detached are still capable of causing stings for 2 weeks or more. Jellyfish stings sometimes occur in fresh water as well.
Signs & Symptoms
A jellyfish itself consists of a bell shape with suspended tentacles. They open and close their bell-like body to drift and slowly swim in the water.
The sting of a jellyfish may appear swollen, red, and bleeding. The affected area may burn and feel painful.
Additionally, the person who has been stung by a jellyfish may experience the following:
Nausea or vomiting
Pain in unaffected areas, such as the groin or armpit
The rescuer should take care to avoid injury by wearing gloves and protective clothing or any readily available barrier.
Remove the affected individual from the water.
Wipe stingers or tentacles off with a towel.
Wash the affected area with salt water.
Some self-care measures will help some jellyfish stings but will cause an adverse reaction in other types. For that reason, the following should be avoided without advice from a medical professional.
DO NOT wash or soak the affected area with fresh water if the injury occurred in salt water.
DO NOT apply vinegar, urine, alcohol, or meat tenderizer/water solution to the affected area.
DO NOT rub the affected area.
DO NOT raise the affected area above the level of the heart.
DO NOT give the person medication.
When to Seek Medical Care
Seek medical care if the person is having difficulty breathing, is bleeding profusely, or other body-wide (generalized) symptoms are occurring, such as the following:
Nausea or vomiting
There is pain in an area not directly affected by the jellyfish sting, such as the groin or armpit
In the case of some jellyfish stings, such as a sting from the box jellyfish of Australia, an antivenin may be necessary to treat the symptoms of anaphylactic shock.
The treatment may vary depending on the type of jellyfish sting. General treatment measures for most jellyfish stings are as follows:
Immerse the sting area in hot water until pain is relieved.
Remove tentacles (if still present) with forceps.
Remove stingers (nematocysts) with shaving cream and a razor.