Common house spiders can carry harmful bacteria that can be transmitted to people through bites, according to research by scientists at NUI Galway.
The research found that the Noble False Widow spider also carries harmful bacteria strains, which are resistant to common antibiotics.
The study, published in the international journal Scientific Reports, explains a range of symptoms experienced by people who have been bitten by the Noble False Widow spider in Ireland and the UK over the past ten years.
Australian Black Widow or Funnel Web spiders are known for their potentially deadly venom.
Rare "skin-eating" conditions, which followed seemingly harmless European and North American spider bites, were thought to have been the result of secondary infections caused by the person scratching the bite area.
However, the research shows that not only do spiders carry harmful bacteria, but the germs can be transmitted when the spider uses its fangs to bite.
NUIG zoologist Dr Michael Dugon said there has been an increase in bite reports over the past five years and some victims complained about "deep infections".
Speaking on RTÉ's Morning Ireland, he said the team found 22 different species of bacteria and some of these are resistant to antibiotics.
He said most of the people who reported bites were bitten in their bed or when getting dressed in the morning.
There are around ten species of common spiders in northwestern Europe with fangs strong enough to pierce human skin.
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Dr John Dunbar, Zoologist at the Ryan Institute's Venom System Lab in NUI Galway, said only the Noble False Widow spider is considered of medical importance.
He said that most of the time a spider bite results in some redness and pain, but in some cases a person can develop long lasting infections, which need strong antibiotic treatment and possibly hospitalisation.