Find information on medical topics, symptoms, drugs, procedures, news and more, written in everyday language.

* This is the Consumer Version. *

Marine Animal Stings and Bites

by Robert A. Barish, MD, MBA, Thomas Arnold, MD

A variety of marine animals sting or bite.


Stingrays contain venom in spines located on the back of their tail. Injuries usually occur when a person steps on a stingray (which is often buried in sand) while wading in shallow ocean surf. The stingray thrusts its tail spine into the person’s foot or leg, releasing venom. Fragments of the spine’s covering may remain in the wound, increasing the risk of infection.

The wound from a stingray’s spine is usually jagged and bleeds freely. Pain is immediate and severe, gradually diminishing over 6 to 48 hours. Many people with these wounds experience fainting spells, weakness, nausea, and anxiety. Vomiting, diarrhea, sweating, generalized cramps, breathing difficulties, and death are less common.


Stingray injuries to an arm or leg should be gently flooded with salt water in an attempt to remove fragments of the tail spine. The spine should be removed only if it is at the skin surface and is not penetrating the neck, chest, or abdomen. Significant bleeding should be slowed by applying direct pressure. In the emergency department, doctors examine the wound for fragments of the spine. A tetanus shot may be needed, and the injured arm or leg should be elevated for several days. Some injured people are given antibiotics and may need surgery to close the wound.


Jellyfish belong to a group known as Cnidaria. Other Cnidaria include

  • Sea anemones

  • Corals

  • Hydroids (such as the Portuguese man-of-war).

Cnidaria have stinging units (nematocysts) on their tentacles. A single tentacle may contain thousands of them. The severity of the sting depends on the type of animal. The sting of most species results in a painful, itchy rash, which may develop into blisters that fill with pus and then rupture. Other symptoms may include weakness, nausea, headache, muscle pain and spasms, runny eyes and nose, excessive sweating, and chest pain that worsens with breathing. Stings from the Portuguese man-of-war (in North America) and the box jellyfish (in Australia in the Indian and South Pacific oceans) have caused death.


The first step in treating an injury caused by a jellyfish in the oceans of North America is rinsing with seawater to wash away venom from the skin. Any pieces of tentacles should be removed with tweezers or, after two pairs of gloves are put on, fingers. Vinegar should not be used as a rinse on injuries from the Portuguese man-of-war because it can cause additional venom to be released from nematocysts that have not yet stung (“unfired" nematocysts). In contrast, vinegar should be used for stopping additional “firings” of nematocysts from the more dangerous box jellyfish. Seawater should be used to rinse box jellyfish stings because fresh water will cause additional venom to be released.

For all types of stings, hot or warm water soaks or cold packs, whichever feels better to the person, can help relieve pain. At the slightest sign of breathing problems or altered awareness (including unconsciousness), medical help should be sought immediately.

Seabather's eruption

Seabather’s eruption is a stinging, itchy rash that affects swimmers in some Atlantic locations (such as Florida, the Caribbean, and Long Island). It is caused by an allergic reaction to stings from the larvae of the sea anemone or the thimble jellyfish. The rash appears where the bathing suit contacts the skin. People who suspect they have been exposed to these larvae should shower after taking off their bathing suit. Rashes can be treated with hydrocortisone lotion and, if needed, an oral antihistamine. If the reaction is more severe, people may need to seek medical help.


Mollusks include snails, octopuses, and bivalves (such as clams, oysters, and scallops). A few are venomous. The California cone ( Conus californicus ) is the only dangerous mollusk in North American waters. Its sting may cause pain, swelling, redness, and numbness in the area of the sting and may rarely be followed by difficulty speaking, blurred vision, paralysis of muscles, difficulty breathing, and low blood pressure. The bites of North American octopuses are rarely serious. However, the bite of the blue-ringed octopus—present in Australian waters—although painless, causes weakness and paralysis that may be fatal.

Cone snails are a rare cause of envenomation among divers and shell collectors in the Indian and Pacific oceans. The snail injects its venom through a harpoon-like tooth when aggressively handled (for example, during shell cleaning or when placed in a pocket). The venom can cause temporary paralysis that is fatal on rare occasions.


Cone snail stings can be immersed in warm water. First-aid measures seem to provide little help for injuries from California cone stings and blue-ringed octopus bites. If people with any type of mollusk envenomation develop trouble breathing, immediate medical help should be sought.

Sea Urchins

Sea urchins are covered with long, sharp, sometimes venom-coated spines. Touching or stepping on these spines typically causes a painful puncture wound. The spines commonly break off in the skin and cause chronic pain and inflammation if not removed. Joint and muscle pain and rashes may develop.

Sea urchin spines should be removed immediately. Because vinegar dissolves most sea urchin spines, several vinegar soaks or compresses may be all that is needed to remove spines that have not penetrated deeply. Surgical removal may be required for imbedded spines. Soaking the injured body part in hot water often relieves the pain.

Resources In This Article

Drugs Mentioned In This Article

  • Generic Name
    Select Brand Names