Five people have been hospitalised after being stung by a Lion's Mane jellyfish in recent weeks.
The sting is not fatal, but pain can radiate to other parts of the body as well as the affected area.
An above average number of Lion's Mane jellyfish have been recorded close to high population areas recently.
The season for them is between June and September and they are often found in cooler water.
Research published by NUI Galway and UCC shows rinsing with vinegar and then applying a heat pack for 40 minutes is the best treatment.
Hotspots for Lion's Mane jellyfish include Forty Foot diving area in Dun Laoghaire and popular beaches like Bettystown, Co. Meath and Clogherhead, Co. Louth.
Recent sightings were reported in Salthill, Kinvara, Carna and Oranmore in Galway as well as Newquay in Clare and Cork harbour.