Paul Gatt MD, FRCP (Edin)
Consultant Dermatologist

For the second year running, and much to the dismay of locals and tourists alike, our beaches are infested by the Mediterranean Mauve Stinger, Pelagia noctiluca, so called because it is a purple coloured, open sea (pelagic) jellyfish which exhibits a weak bioluminescence and therefore shines with a faint green light in the dark. By popular account, this seems to be a particularly bad year, and jellyfish stings are increasingly being attended to by family physicians, and occasionally by dermatologists. A number of articles on the subject have appeared in the local press (eg: Gatt M.; Grech S.; Lindsay D.; Schembri PJ.)

This is by no means the first time that such infestations have occurred in recent years. Between 1980 and 1983 Axiak et al. (1991) recorded massive aggregations of this species in local waters, with densities of up to 30 individuals m-3 in the sea and 50 individuals m-2 on shore.

Jellyfish populations bloom whenever their food (small planktonic animals in the case of the Mauve Stinger) is in good supply. Winds then generate sea currents which propel the animals to the coast, where they may remain trapped in embayments by circular currents until the wind changes and carries them away.

The tentacles of jellyfish are equipped with stinging cells (cnidocytes). Each cnidocyte contains a stinging unit called a nematocyst. Upon stimulation, the nematocyst is activated, bursts open and fires a hollow barbed thread into the skin. A variety of toxins (including catecholamines, histamine, serotonin, collagenases, hyaluronidases, proteases,

phospholipases, fibrinolysins, neurotoxins, nephrotoxins, myotoxins and antigenic proteins) are then injected into the skin through this hollow shaft. The effects of the sting vary according to the number of nematocysts that are activated, the species of jellyfish involved, the part of the skin that is stung, and the sensitivity of the victim to the toxins injected. They vary from a painful, red, raised cutaneous lesion which later vesiculates, to anaphylactic shock and death. Stings to the eyes are particularly severe.

Dead jellyfish stranded on the shore, unless desiccated, are capable of delivering stings for several days.

A number of remedies (Table 1) have traditionally been touted as first aid treatment for ‘jellyfish stings’, the purpose of each being to inactivate undischarged nematocysts and prevent further injection of toxin into the body.

First Aid Treatment of Jellyfish stings

  • Sea water
  • Sterile saline
  • Vinegar (5% acetic acid)
  • Baking soda
  • Isopropyl alcohol
  • Papain (meat tenderizer)
  • Urine

Do any of these remedies work?

Very few scientific studies on the effect of any of these agents have in reality been carried out, so the data is mostly anecdotal and handed down from one generation to another. Most studies originate from America and Australia, and many deal with Australian species of jellyfish. Jellyfish from other regions respond differently to different measures because they have different physiologies and elaborate different toxins. For example, vinegar effectively inactivates nematocysts from potentially deadly Cubozoan jellyfish (unlikely to be encountered in Maltese waters) but triggers them off in other species (Fenner et al.). First aid measures to prevent additional nematocyst rupture appears to be species specific (Burnett et al, 1986). In this case at least, what is good for the goose is not necessarily good for the gander. The question ‘what is good for a jellyfish sting’ would therefore appear to be as inane as asking ‘what is good for a bacterium’

without specifying whether it is Gram-negative or Gram-positive, coagulase negative or positive and so forth. Isopropyl alcohol tends to make matters worse, and urine has fallen out of favour.

Do any of these remedies work for Pelagia noctiluca stings?

Again, no proper studies have been carried out, so the bottom line is that we do not know. In this situation, the best strategy is to employ an evidence based, minimalistic approach which at best alleviates the symptoms and does not make them worse. To my knowledge, anaphylaxis has never been reported with Pelagia noctiluca stings, although they may be severe, painful and complicated (Table 2).

Complications of Pelagia noctiluca stings

  • Secondary infection
  • Scarring, including keloid formation
  • Pigmented striae
  • Ulceration and necrosis
  • Granuloma formation
  • Lichenification from persistent rubbing

What then, does one do – or not do?

Management of jellyfish stings is targeted towards nematocyst inactivation, pain control and local wound care.

Rubbing the skin over the affected area will cause further nematocysts to discharge and should be avoided. Similarly, fresh water (or ice) will enhance nematocyst activation and should not be used on the wound.

Any adherent tentacles should first be lifted off, ideally with a pair of forceps, and not scraped. The area should then ideally be copiously irrigated with sterile saline which will inactive any nematocysts still adherent to the skin. Since not everybody packs sterile saline into their beach bags, sea water may have to do, but this risks introducing marine pathogens into the wound.

In the event that nematocysts still adhere to the wound after irrigation, then it probably does no harm to cover the area with an aerosol spray shaving cream and shave them off with a razor blade or credit card edge.

Ice packs, firmly applied to the wound and held there for 10 minutes are effective in relieving pain. Condensation on the surface of the pack must not be allowed to accumulate, as this effectively delivers fresh water to the wound. Ice should not be applied to the wound, as the fresh water from the melting ice will activate undischarged nematocysts. There is no evidence that topical anaesthetics, like benzocaine or lidocaine, reduce pain more then ice packs do. Heat should not be applied to the wound as this increases systemic absorption of toxin.

After care.

It is reasonable to expect a combined topical steroid/antibiotic combination to reduce inflammation and prevent secondary bacterial infection. Tetanus prophylaxis should be given. Oral analgesics are effective in reducing pain, and oral antibiotics should be used if secondary bacterial infection supervened. On no account must the wound be exposed to sunlight, as this will almost certainly result in severe, persistent post-inflammatory hyperpigmentation which is very difficult to treat.

References

Axiak V, Galea C, Schembri P J. Coastal aggregations of the jellyfish Pelagia noctiluca (Scyphozoa) in Maltese coastal waters during 1980-1986. MAP Tech. Rep. Ser. 1991; 47:32-40.

Burnett JW, Calton GJ, Burnett HW. Jellyfish envenomation syndromes. JAAD 1986; 14(1):100-6.

Burnett J W, Rubinstein H, Calton GJ. First aid for jellyfish envenomation. South Med J. 1983; 76(7):870-72.

Fenner PJ, Williamson JA, Burnett JW, Rifkin J. First aid treatment of jellyfish stings in Australia. Response to a newly differentiated species. Med J Aust 1993; 158(7):498-501.

Gatt M. Jellyfish invasion. The Sunday Times. June 11 2006.

Grech S. No treatment for jellyfish. The Malta Independent on Sunday. June 18 2006.

Lindsay D. No controlling or predicting jellyfish infestations. The Malta Independent on Sunday. June 18 2006.

Rosson CL, Tolle SM. Management of Marine Stings and Scrapes. West J Med 1989; 150(1):97-100.

Schembri PJ. How jellyfish sting. The Malta Independent on Sunday. Submitted.

Acknowledgements

I wish to thank Professor P. J. Schembri of the Biology Department, University of Malta, for generously enlightening me on jellyfish, cnidocytes, and nematocysts.