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Separating myth from reality. It seems to happen several times a year now, a gruesome image of a badly infected leg, arm or hand in the national papers with a spider bite stated as the cause.  

But when you look into the details, you often discover the victim never saw the spider bite them “it bit me whilst I was sleeping” or the spiders are described as acting aggressively (no British spider is aggressive towards humans) and then when you examine the symptoms and their timings, it just doesn’t add up. It seems too easy to blame spiders for bacterial infections.

Noble False-widow (Steatoda nobilis) © Neil Manito

Professor David Lalloo, of Liverpool School of Tropical Medicine, said: “These spiders are not aggressive and bites from them are not dangerous; they may cause short-lived pain and in rare cases, may make people feel unwell for a day or so, but there is no record of them causing serious illness or death.” 

So here are some facts about spiders and their bites.

  • The majority of British spiders could not bite you if they tried because their fangs are too small or weak to be able to penetrate human skin.
  • Even if one of the larger spiders does manage to bite you, the symptoms are usually like a pin prick or milder than a wasp or bee sting and do not last long.
  • Most large spiders are not inclined to bite a human – you can handle hundreds of large house or garden spiders and never get bitten.
  • The notorious Noble false-widow (Steatoda nobilis) does indeed have a more venomous bite than other British species.  It injects a neurotoxin which may cause localised pain, minor swelling, and in extreme cases nausea within a few hours (but not days). Symptoms then fade away. 
  • There are no proven cases where the Noble false-widow has caused death, coma or permanent injury.
  • Its neurotoxins do not result in ‘necrosis’ i.e. the gangrene-like infections described in the media – this results from a bacterial infection which could come from any source including scratching a mosquito bite, scratch or splinter wound with dirty fingers.
  • While an allergic reaction to a spider bite is theoretically possible, this has never been recorded, even in people who are allergic to bee or wasp stings.
  • There is no proven link between spider bites and bacterial infection and there are still no confirmed cases of serious injury resulting directly from the bite of a native spider in Britain
  • Females of the Noble false-widow spider are notably sluggish, ponderous, solitary and non-aggressive, they will never run or jump at you in an aggressive manner as some people have described.
  • Sometimes venomous spiders are introduced with produce or goods from abroad.  Spiders in grocery areas of shops should be treated with caution.

 

What to do if you are bitten:

  • If you are unlucky enough to get bitten by a spider, stay calm - anxiety or panicky reactions are likely to be more harmful than the bite.
  • If you do get significant swelling, cramps, nausea or other symptoms you should seek immediate medical advice – just to be on the safe side.
  • Keep the area around the bite clean and do not scratch the bite (or any insect bite/scratch/puncture wound) as this can cause a bacterial infection. Serious infections develop over days not hours, well beyond the timescale for the effects of neurotoxins.

    Garden cross spider (Araneus diadematus) © Steven Falk

  • If you reckon a spider has bitten you and you can see it, try to catch it in a container – be careful not to be bitten again.  If you then get any symptoms, experts can check the identity. Several types of medium to large spiders, less toxic than Noble false-widow, regularly occur in and around houses and the chances are it will be one of these, especially away from south England. 
  • The above advice is particularly pertinent if handling goods recently imported from tropical areas, but even then bites from even the most venomous species are very unlikely and death or long-term injury from such a bite is exceedingly rare.

Spotting dubious ‘killer spider’ scare stories in the media

Look out for the following indications:-

No spider - it attacked at night, no perpetrator observed – spiders bite when trapped or squeezed, when you are asleep you are generally still and unlikely to harass a spider - plays on vampire fears.

‘Antibiotic prescription’ – the doctors clearly thought it was a bacteria infection or they would have used anti-venom.

‘Killer’, etc. – spiders leaping at, running at and generally being vicious towards people – only happens in the films.

‘Cutting out venom’ – not a treatment for a spider bite, a treatment for necrosis, usually caused by a bacterial infection.

Late response – if the symptoms are worse on day two than day one then venom is unlikely to be the cause – venom has evolved to act quickly.

Unidentified spider picture – journalist has not even bothered to ask an expert to help name the spider in the photo.

‘False widow’ – unspecific references to ‘false-widows’ there are several species of false widow in Britain, including the Common false-widow (Steatoda bipunctata) that lives around human settlements for thousands of years and has never caused anyone any problems (and the most likely to be seen in the north). 

‘A nest of spiders’ – spiders in the UK do not live in ‘nests’, although there are some amazing species in the tropical jungles that do cooperate with each other to build large communal webs.

 And finally…

Please remember that spiders are amazing animals that play an important ecological and environmental role.  Without spiders there would be more flies in your house.  You will achieve very little by squishing spiders.

 

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