A jellyfish is a marine invertebrate that captures and neutralizes its prey with long, trailing tentacles. These tentacles are equipped with nematocysts, small capsules of poison that the jellyfish uses to sting its prey. A sting can be irritating, or it can bring about a life threatening condition. In either case, if you're stung by a jellyfish, get to dry land, gently remove the tentacle, and rinse the area where you were stung with seawater or vinegar.
If you encounter a jellyfish, the first thing to do is to get out of the water. Additional jellyfish may be floating around, and you want to minimize further contact with their venom-laden tentacles. In addition, a patient on dry land is much easier to treat. If a lifeguard is present, notify him or her about the sting. The lifeguard may be able to assist with treatment, and he or she may want to evacuate the water in the area if large numbers of jellyfish have appeared.
In many cases, the tentacle will still be attached to the patient. It will actually continue stinging until it is removed, but it must be removed with care. The stinging capsules on the tentacle can rupture if they are not deactivated, increasing the severity of the sting. If you have vinegar available, pour it liberally over the affected area. Seawater will work as well for this, but it is less effective. Next, remove the tentacle, making sure that it does not touch bare skin. Wear gloves, or if gloves are not available, use tweezers, a towel, or even a piece of seaweed.
Once the tentacle has been removed, the area should be rinsed again with vinegar or seawater. A paste of baking soda can also be applied and left on, or a meat tenderizer can be used, as long as it is left on for less than 15 minutes. After the area has been thoroughly rinsed, check for signs of lesions or hives. Antibiotic ointment can be applied to cuts, while hydrocortisone cream can reduce itching. It may take several weeks for the patient to completely recover after being stung by a jellyfish, but as long as the injured area appears to be looking better every day, it is not a cause for concern.
There are a few cases in which someone who has been stung will need emergency medical attention. If the patient is very young, very old, or has severe allergies, take him or her to a medical professional as soon as possible. Vomiting, spasms, difficulty breathing, or an altered level of consciousness are also indicators that someone has received a severely toxic sting. If the person appears to be taking a long time to recover from being stung by a jellyfish, or the symptoms get worse at any point, it is important to take them to a medical provider.