A Galway-based spider expert is asking anyone who has been bitten by the False Widow spider to contact his laboratory.
The appeal comes following recent reports on WLR fm in Waterford of people suffering symptoms from the spiders' bite.
The False Widow comes from the Canary Islands and looks very similar to a Black Widow spider.
Dr Michel Dugon, principal investigator of the Venom Systems Lab at NUIG, says they have been reported in at least 18 counties in Ireland.
Speaking on RTÉ's News At One, he said the spider arrived here in the 1990s and were first recorded in Bray, Co Wicklow.
He said that because they come from a Mediterranean climate, they do not survive in the Irish countryside, but that they do "amazingly well" in urban environments.
Dr Dugon says that the False Widow's bite can be quite painful.
Experts @nuigalway @VenomSyst say False Widow is size of 2 euros coin and not dangerous unlike Black Widow with distinctive red belly and found mainly in Nth America @rtenews #spiders #falsewidow pic.twitter.com/zSJRc583U5— TERESA MANNION (@TeresaMannion) July 18, 2019
"It seems from the cases that we've studied so far that the bite is actually fairly painful.
"Most victims say that very quickly after the bite, they felt a very sharp and intense pain. In most cases, victims will complain of fairly mellow symptoms, but we do have some patients who complain of swelling, goosebumps, chills, sweats and fever."
He said a bite from a False Widow has not killed anyone as far as he is aware, whereas a sting from a bee or wasp can be fatal to some people.
He said False Widows are not aggressive and only bite when they feel threatened.
"If a False Widow is squeezed between your skin and your clothes, it will defend itself because it thinks it's under attack. If a spider happens to be in your bed and you turn over and squeeze it between your bed sheet and skin, it will bite."
Dr Dugon said that because the bites are usually accidental, it can be hard to avoid them.
He said that the False Widow is now so widespread in towns and cities that it would be extremely difficult to get rid of it.
His advice for those who do get bitten is to monitor the bite and try and capture the spider.
He said they need to be able to identify the spider to ensure that it is a False Widow bite.
He said that if a victim feels anything more than "just a bit of pain and redness", then they should contact a doctor.
Maria Condon from Co Waterford was bitten by a spider, and spent a number of days in hospital.
She said it bit her while she was at home in her living room, and described it as 'boiling water being poured over my leg'.
She told RTÉ News that painful blisters started appearing within minutes, and that they got worse over the next hour.
She said she was awake all night with pain and went to the doctor the following morning. He gave her an antibiotic and marked her leg, telling her to come back if the redness went past the marking.
Ms Condon said she went back two days later and her leg was marked again, and she later ended up in A&E.
She was given more antibiotics and ointment, but was eventually admitted to hospital. She is now back home but says a number of her blisters haven't fully faded.
Ms Condon said she found a nest of spiders in her living room when she returned home, and has contacted an exterminator.
Cormac Melia from Co Laois says his three-year-old son Noah was bitten on the leg by a spider three weeks ago and is still suffering from the effects.
He said he gave the toddler an antihistamine, but that his leg was red and swollen by the evening.
"It looked kind of like a hive. It wasn't a blister, but it looked kind of like a blister. We put on some sudocream and thought it would be ok by the morning, but it had turned into a big bubble. It burst an hour or two later."
Mr Melia said Noah couldn't walk properly and was in pain. He said they brought the toddler to a doctor after another blister formed around the one that had burst.
He said the doctor told them an infection had formed due to an insect bite, and Noah was put on antibiotics and a steroid cream.
He said it's been three weeks and the redness is still there, and he believes it will leave a scar.