Jellyfish is a term used to describe a number of marine creatures that possess long tentacles and a transparent body 2. There are four major types of jellyfish--lion's mane, Portuguese man-of-war, sea nettle and sea wasp. The tentacles of jellyfish contain stinging cells that can cause significant injury to humans and other animals 2. Jellyfish sting side effects in humans vary based on the type of jellyfish a person comes in contact with.

Skin Rash

After being stung by a jelly fish, patients can develop a red, irritated skin rash at the site of the sting. A sting from a sea nettle generally results in mild skin-rash symptoms. Patients stung by lion's mane, sea wasp or Portuguese man-of-war can develop severe skin-rash symptoms that can include blistering, pain or swelling near the site of the sting. Certain patients may also experience sensations of burning or stinging that extend into the skin surrounding the sting site. These side effects require immediate medical attention and may persist for several days.

Muscle Cramps

A jellyfish sting can cause side effects of muscle cramping in affected patients, according to Medline Plus, a medical information website supported by the National Institutes of Health 2. Muscle cramps can be uncomfortable and may persist for several hours until the jellyfish sting is treated.

Nausea or Vomiting

Patients stung by a jellyfish can experience stomach upset side effects within minutes of injury. These stomach-related side effects can include nausea or vomiting, which may occur in conjunction with diarrhea. Certain patients can also develop a fever or begin to sweat profusely. Patients who develop any of these jellyfish side effects should be taken to an emergency medical care clinic or hospital as soon as possible 2.

Breathing Difficulty

Breathing difficulties can arise in patients who are stung by sea wasp or lion's mane jellyfish, according to, a peer-reviewed medical information website 2. Shortness of breath or wheezing may also occur in conjunction with chest discomfort. These potentially life-threatening side effects of a jellyfish sting require emergency medical intervention.

Heart Rate Abnormalities or Chest Pain

A sting from a Portuguese man-of-war, sea nettle or sea wasp can cause heart-related side effects. Within minutes of being stung, a patient can develop an abnormally slow heart rate or pulse. Certain patients may also experience chest pain in conjunction with these side effects. These patients require immediate emergency medical care to prevent further medical complications.

Weakness or Loss of Consciousness

A patient who is stung by a jellyfish can become unusually weak, lightheaded or dizzy. These jellyfish side effects may cause an affected patient to collapse, faint or lose consciousness 2. A severe jellyfish sting can cause temporary paralysis. If any of these side effects occur, take the affected patient to an emergency room immediately.