Spider bites can be painful, but most are harmless and need no treatment. Species that can be dangerous to humans include members of the genus Latrodectus (including the infamous black widow of North America), the Australian funnel web spider, the Brazilian wandering spider and the recluse spiders of the Americas and Africa.
Medical Management of Spider Bites
Spiders seldom attack humans on purpose, but may bite when they feel threatened. The best way to avoid spider bites is, therefore, to avoid spiders. Cover up when working in sheds, attics and other places where spiders may live, seal cracks and crevices where spiders might enter the house, and never attempt to provoke or handle spiders in the wild.
Bites generally occur when a spider is disturbed accidentally. There is usually no need to seek medical attention. Spider bites are rarely fatal or even troublesome in humans – in most cases, the amount of venom released is simply too small to have much effect. However, people who suspect they have been bitten by a dangerous species, or who suffer severe pain or cramps in the abdomen or back after a bite, should consult a doctor promptly.
In addition to thorough cleaning of the wound, ice packs and painkillers, the doctor may give antivenom for a black widow bite, or a drug called dapsone that prevents the tissue death (necrosis) caused by recluse spider venoms.
Difficulties with the Diagnosis of Spider Bites
Although it might be obvious that a spider bite has occurred – if the biting is witnessed by the victim or another person, for example – this is not always the case. The pain and necrosis associated with recluse spider venoms are slow to appear, and diagnosis and treatment of bites from these species may be delayed as a consequence.
Conversely, it is easy to mistake other conditions for spider bites. A recent paper published in The Lancet (Ibister & Hui, 2011) suggests that many primary care and emergency department physicians are unfamiliar with genuine spider bites, and as a result may blame any area of skin necrosis on an arachnid attack.
As the authors point out, most cases of skin necrosis are not due to spider bites. Bacterial skin infections and Lyme disease, for example, are much more common. People with another condition who are misdiagnosed as having been bitten by a spider may be given unnecessary antivenom, which is wasteful of resources and can cause an allergic reaction. Meanwhile, the true cause of their symptoms goes unrecognized.
Misdiagnosis of Spider Bites can be Life-threatening
Ibister and Hui suggest that more case reports of confirmed spider bites should be published in the medical literature, to increase doctors’ familiarity with the symptoms and reduce the potentially life-threatening risks of misdiagnosis. However, anyone who thinks they might have been bitten by a venomous spider should not hesitate to seek medical help, as prompt treatment for the effects may be crucial.
Sources
Isbister GK, Hui WF. Spider Bite. Lancet 2011, doi:10.1016/S0140-6736(10)62230-1 Accessed 26-07-11
Mayo Clinic. Spider Bites. Accessed 26-07-11
Medline Plus. Skin Lesions Often Misdiagnosed as Spider Bites. Accessed 26-07-11
Disclaimer
The information contained in this article is for educational purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or her health should contact a doctor for advice.
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