In the UK, spiders are not normally thought of as hazardous to health. So it may come as a surprise that a dozen or more species resident in the UK are capable of causing a significant or unpleasant bite.
The incidents quoted below are all considered to have been genuine cases of spider bite. They are cases where the specimen was submitted for identification to the Natural History Museum, and accompanied by an account of the bite and its symptoms.
Typical symptoms of a spider bite in the UK are local pain, swelling and reddening. Countrywide, the incidence of bites is not high (perhaps a number in 10s or 100s each year) but, with the relatively recent spread in the UK of some colonising species, the frequency appears to be increasing. However, there are no statistics collected nationwide. Thus reports help alert people, including medical practitioners, to the reality that the UK has a number of spiders that can and do cause bites.
In this country, 90 to 100 per cent of the bite cases are caused by no more than 12 of the approximately 700 native species. Of all the remaining species, the great majority are quite harmless, in spite of having venom, and have no history of biting humans. Furthermore, the increase in bite cases is believed to be linked to just 2 species of exotic spiders that have become established here and are now spreading widely.
The spiders that have recently colonised this country have done so in one of two ways. Either they have been transported here via imported goods, or they have introduced themselves, quite naturally, as part of a northward migration within Europe. In their original territory they tend to live in the open, But, in the colder climate of the UK, they adapt readily to sheltered, urban environments. Thus they occur in and around buildings, with inevitably close contact to humans.
When considering spider bites, caution is necessary because it is well known that spiders often get the blame for bites and stings that are actually caused by insects or even plants. Nevertheless, the incidents quoted in this report are all considered to have been genuine cases of spider bite.