Evaluation of the Effects of Various Chemicals on Discharge of and Pain Caused by Jellyfish Nematocysts

Portuguese Man-of-War (Physalia physalis).

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This study evaluated the effect of well-known remedies on the discharge of nematocysts in three species of Cnidarians: the sea nettle (Chrysaora quinquecirrha), sea wasp (Chiropsalmus quadrumanus) and the Portuguese man-of-war (Physalia physalis).  The remedies tested include acetic acid, ammonia, meat tenderizer, baking soda, and urea.  These remedies were evaluated to determine whether they stimulated or inhibited nematocyst discharge and if they brought relief to testers who were exposed to jellyfish tentacles.  It was found that many of the remedies did not relieve the pain and it actually stimulated nematocyst discharge.  However, immediate relief was experienced with lidocaine, a common anesthetic.  Exposure of the tentacle to lidocaine prevented nematocyst discharge when preceding exposure to acetic acid, ethanol, ammonia or bromelain.  Based on these observations, it is possible that lidocaine blocks the sodium and/or calcium channels of the nematocysts, preventing discharge.  The nematocysts of organisms in Phylum Cnidaria are hollow tubules in a saline solution containing neurotoxins.  Typical symptoms of jellyfish stings include pain, localized areas of swelling, redness and bleeding.  Used for defense, both mechanical and chemical stimuli cause nematocysts to be discharged.  With an increase in the number of envenomations in coastal beaches around the world, this study aimed to answer the question if traditionally used methods have effect on nematocyst discharge or if they dampened the pain associated with being stung.

Specimens were collected in coastal waters and tentacles were clipped and transferred to seawater.  These tentacle pieces were added to wells containing 1mL of seawater and examined under a light microscope.  To determine whether the chemical remedies had an effect on the nematocysts, 100µL of each chemical was added and observations were noted.  In a separate experiment, lidocaine was first added to the wells and then after one minute, each chemical was added in separate well plates.  A camera was attached to the light microscope to capture nematocyst discharging, and discharged nematocysts were counted.

During the human skin exposures, sea nettle and sea wasp tentacles were used.  Two of the authors exposed their inner arm to the tentacles over a period of 20 days with only one treatment per day.  Observations of skin redness before and after the addition of chemicals were made by outside observers.  Notes were taken of the stinging sensation as well. 

It was determined that chemicals traditionally used to treat jellyfish stings were found to stimulate nematocyst discharge and provided little or no relief from the pain and stinging sensation.  Lidocaine appears to provide relief by acting as an anesthetic and by preventing further nematocyst discharge.  Although blocking the pain, it did not prevent redness on the skin.  Also, when first applying lidocaine, then acetic acid or ammonia, the nematocyst discharge was prevented.  Overall, the best treatment option for jellyfish stings appear to be with the anesthetic lidocaine, as it blocks sodium ion channels in nerves that sense pain.            

Reference:

Birsa, L. M., Verity, P. G., & Lee, R. F. (2010). Evaluation of the effects of various chemicals on discharge of and pain caused by jellyfish nematocysts. Comparative Biochemistry and Physiology:Toxicology and Pharmacology, 151, 426-430.