Jellyfish venom, which contains several chemicals including neurotoxic peptides

Types of potentially harmful jellyfish include:

• Lion's mane (Cyanea capillata).
• Portuguese man-of-war (Physalia physalis in the Atlantic and Physalia utriculus in the Pacific).
• Sea nettle (Chrysaora quinquecirrha), one of the most common jellyfish found along the Atlantic and Gulf coasts.
• Box jellyfish (Cubozoa) all have a box-like body or "bell" with tentacles extending from each corner. There are over 40 species of box jellies. These range from nearly invisible thimble-sized jellyfish to basketball-sized chirodropids found near the coasts of northern Australia, Thailand, and the Philippines (Chironex fleckeri, Chiropsalmus quadrigatus). Sometimes called sea wasps, box jellyfish are highly dangerous, and more than 8 species have caused deaths. Box jellyfish are found in the tropics including Hawaii, Saipan, Guam, Puerto Rico, the Caribbean, and Florida, and recently in a rare event in coastal New Jersey.

There are also other types of stinging jellyfish.

If you are unfamiliar with an area, be sure to ask local ocean safety staff about the potential for jellyfish stings and other marine hazards. In areas where box jellies may be found, especially at sunset and sunrise, full body coverage with a stinger suit, hood, gloves, and booties is advised.

Symptoms of stings from different types of jellyfish are:

LION'S MANE

• Breathing difficulty
• Muscle cramps
• Skin burning and blistering (severe)

PORTUGUESE MAN-OF-WAR

• Abdominal pain
• Changes in pulse
• Chest pain
• Chills
• Collapse (shock)
• Headache
• Muscle pain and muscle spasms
• Numbness and weakness
• Pain in the arms or legs
• Raised red spot where stung
• Runny nose and watery eyes
• Swallowing difficulty
• Sweating

SEA NETTLE

• Mild skin rash (with mild stings)
• Muscle cramps and breathing difficulty (from a lot of contact)

SEA WASP OR BOX JELLYFISH

• Abdominal pain
• Breathing difficulty
• Changes in pulse
• Chest pain
• Collapse (shock)
• Headache
• Muscle pain and muscle spasms
• Nausea and vomiting
• Pain in the arms or legs
• Raised red spot where stung
• Severe burning pain and sting site blistering
• Skin tissue death
• Sweating

For the great majority of bites, stings, or other forms of poisoning, the danger is either drowning after being stung or an allergic reaction to the venom.

Seek medical help right away. Get medical attention right away if pain increases or there are any signs of breathing difficulty or chest pains.

• As soon as possible, rinse the sting site with large amounts of household vinegar for at least 30 seconds. Vinegar is safe and effective for all types of jellyfish stings. Vinegar rapidly halts the thousands of tiny unfired stinging cells left on the surface of the skin after tentacle contact.
• If vinegar is not available, the sting site can be washed with ocean water.
• Protect the affected area and do not rub sand or apply any pressure to the area or scrape the sting site.
• Soak the area in 107°F to 115°F (42°C to 46°C) standard tap hot water, (not scalding) for 20 to 40 minutes.
• After soaking in hot water, apply antihistamine or steroid creams such as cortisone cream. This can help with pain and itching.

Have this information ready:

• Person's age, weight, and condition
• Type of jellyfish, if possible
• Time the person was stung
• Location of the sting

The local poison control center can be reached directly by calling the national toll-free Poison Help hotline (1-800-222-1222) from anywhere in the United States. This national hotline will let you talk to experts in poisoning. They will give you further instructions.

This is a free and confidential service. All local poison control centers in the United States use this national number. You should call if you have any questions about poisoning or poison prevention. It does NOT need to be an emergency. You can call for any reason, 24 hours a day, 7 days a week.

You can also get online poison help now at Poisonhelp.org. Just enter the product, poison, or medicine to get expert help.

Your health care provider will measure and monitor your vital signs, including temperature, pulse, breathing rate, and blood pressure. Symptoms will be treated.

You may receive:

• Antivenin, a medicine to reverse the effects of the venom, may be used for one specific box jelly species found only in certain areas of the Indo-Pacific (Chironex fleckeri)
• Blood and urine tests
• Breathing support, including oxygen, a tube through the mouth into the throat, and breathing machine
• Chest x-ray
• Electrocardiogram (ECG)
• Fluids through a vein (by IV)
• Medicine to treat symptoms

Most jellyfish stings improve within hours, but some stings can lead to skin irritation or rashes that last for weeks. Contact your provider if you continue to have itching at the sting site. Topical anti-inflammatory creams may be helpful.

Portuguese man-of-war and sea nettle stings are rarely deadly.

Certain box jellyfish stings can kill a person within minutes. Other box jellyfish stings can lead to death in 4 to 48 hours after a sting due to Irukandji syndrome, a delayed reaction to the sting.

It is important to carefully monitor box jellyfish sting victims for hours after a sting. Seek medical attention right away for any breathing difficulties, chest or abdominal pains, or profuse sweating.

Curtis AM, Erickson TB. Venomous animal injuries. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 53.

Feng S-Y. Envenomations. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 746.

Scerri L. Jellyfish stings. In: Lebwohl MG, Heymann WR, Coulson IH, Murrell DF, eds. Treatment of Skin Disease: Comprehensive Therapeutic Strategies. 6th ed. Philadelphia, PA. Elsevier; 2022:chap 116.

Updated by: Jesse Borke, MD, CPE, FAAEM, FACEP, Attending Physician at Kaiser Permanente, Orange County, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.