Microscopic jellyfish affecting swimmers at Auckland beaches

24 January 2012

Microscopic jellyfish stings affecting swimmers at Auckland beaches

Following reports of rashes caused by stings from microscopic jellyfish, Auckland Regional Public Health Service is advising swimmers to take care at Hauraki Gulf beaches.

The microscopic jellyfish - or hydromedusae - can cause a red, raised, itchy or painful rash, also known as sea bathers eruption, which tends to mainly affect areas that have been covered by a bathing suit or clothes, rather than uncovered areas. The jellyfish, which are transparent and too small to be seen, get caught inside swimwear. As the bather leaves the water the jellyfish become trapped and sting the areas covered by their swimwear. A tingling sensation is often noticed first. Over several hours, the rash develops.

Medical Officer of Health, Dr Simon Baker says, “The only guaranteed way to prevent being stung is to avoid bathing at affected beaches. We have had reports from Long Bay, Milford and Takapuna beaches, although it is likely that this problem extends all along the Hauraki Gulf”.

Auckland Regional Public Health Service recommends:

• The only certain way to prevent being stung is to avoid swimming at affected beaches, and to swim in a freshwater swimming pool instead
• Do not wear large baggy clothes into the water (but still stay Sunsmart)
• After swimming, remove your swimwear as soon as possible and then shower if you can – especially the area that was covered by your swimwear
• Don’t towel the area before showering – this will just set off the stinging
• If you develop a rash, have a shower, and get into cool loose clothing. Calamine lotion may help
• If the rash persists, visit your local pharmacy – mild steroid creams like hydrocortisone can be helpful, as can antihistamine tablets
• If problems are severe or persist or worsen, see a doctor
• Don’t put the swimwear back on until laundered properly, as the jellyfish can still sting even after they are dead.

Until 2008 these rashes were thought to be caused by sea lice. However, sea lice tend to bite exposed areas of the skin while the jellyfish normally sting underneath swimwear. Jellyfish numbers increase in periods of warm weather.

ENDS