Jellyfish stings occur when a person comes into contact with the tentacles of a jellyfish, which can release venomous cells called nematocysts. These stings can range from mild discomfort to severe pain and can be dangerous in some cases.

Here are some steps to take if you are stung by a jellyfish:

1. Get out of the water: If you are in the water when you are stung, get out as quickly as possible to prevent further stings.
2. Rinse the affected area: Rinse the affected area with vinegar, which can help to neutralize the venom.
3. Remove tentacles: If there are any tentacles still attached to the skin, remove them using tweezers or a gloved hand. Do not use bare hands, as this can lead to further stings.
4. Soak in hot water: Soak the affected area in hot water (110-113°F) for at least 20-30 minutes to help reduce pain and neutralize the venom.
5. Take pain relief medication: Over-the-counter pain relief medication, such as ibuprofen or acetaminophen, can help to alleviate pain.
6. Seek medical attention: If the sting is severe or you are experiencing any symptoms such as difficulty breathing, chest pain, or swelling of the tongue or throat, seek medical attention immediately.

Prevention is key when it comes to jellyfish stings. It is important to wear protective clothing such as wetsuits, avoid swimming in areas with known jellyfish populations, and to be aware of the signs of a jellyfish in the water.

Jellyfish tentacles contain microscopic barbed stingers. Each stinger has a tiny bulb that holds venom and a coiled, sharp-tipped tube. The jellyfish uses the venom to protect itself and kill prey.

When you brush against a tentacle, tiny triggers on its surface release the stingers. The tube penetrates the skin and releases venom. It affects the immediate area of contact and may enter the bloodstream.

Jellyfish that have washed up on a beach may still release venomous stingers if touched.

Types of jellyfish

While many types of jellyfish are relatively harmless to humans, some can cause severe pain and are more likely to cause a systemic reaction. These jellyfish cause more-serious problems in people:

• Box jellyfish. Box jellyfish can cause intense pain. Life-threatening reactions — although rare — are more common with this type. The more dangerous species of box jellyfish are in the warm waters of the Pacific and Indian oceans.
• Portuguese man-of-war. Also called bluebottle jellyfish, Portuguese man-of-war jellyfish live mostly in warmer seas. This type has a blue or purplish gas-filled bubble that keeps it afloat on the water and acts as a sail.
• Sea nettle. Common in both warm and cool seawaters, sea nettles live along the northeast coast of the United States and are abundant in the Chesapeake Bay.
• Lion's mane jellyfish. These are the world's largest jellyfish, with a body diameter of more than 3 feet (1 meter). They're most common in cooler, northern regions of the Pacific and Atlantic oceans.

The following tips can help you avoid jellyfish stings:

• Wear a protective suit. When swimming or diving in areas where jellyfish stings are possible, wear a wet suit or other protective clothing. Diving stores sell protective "skin suits" or "stinger suits" made of thin, high-tech fabric. Consider protective footwear as stings can also occur while wading in shallow water.
• Get information about conditions. Talk to lifeguards, local residents or officials with a local health department before swimming or diving in coastal waters, especially in areas where jellyfish are common.
• Avoid water during jellyfish season. Stay out of the water when jellyfish numbers are high.

Treatment for jellyfish includes first-aid care and medical treatment, depending on the type of jellyfish, the severity of the sting and your reaction to it.

First-aid care

Most jellyfish stings can be treated as follows:

1. Carefully pluck visible tentacles with a fine tweezers.
2. Soak the skin in hot water. Use water that's 110 to 113 F (43 to 45 C). If a thermometer isn't available, test the water on an uninjured person's hand or elbow — it should feel hot, not scalding. Keep the affected skin immersed or in a hot shower for 20 to 45 minutes.

Steps to avoid

These actions are unhelpful or unproved:

• Scraping out stingers
• Rinsing with seawater
• Rinsing with human urine
• Rinsing with fresh water
• Applying meat tenderizer
• Applying alcohol, ethanol or ammonia
• Rubbing with a towel
• Applying pressure bandages

Medical treatment

• Emergency care. Someone having a severe reaction to a jellyfish sting may need cardiopulmonary resuscitation (CPR), life support or, if the sting is from a box jellyfish, antivenin medication.
• Oral medicine. A rash or other skin reaction due to delayed hypersensitivity may be treated with oral antihistamines or corticosteroids. You may also be given oral pain medicine.
• Eye flushing. A jellyfish sting occurring on or near an eye requires immediate medical care for pain control and a good eye flushing. You will likely be seen by a doctor specializing in eye care (ophthalmologist).