Spider Bites

Spiders are dangerous to humans when the former accidentally bite the latter. About 20 species of spiders are known to cause dangerous envenoming of humans. A few species are capable of causing necrotic wounds and, occasionally, death. The only spiders of real medical importance to humans in the United States and in other countries are the Loxosceles and Latrodectus species, primarily the brown recluse and the black widow, respectively. These spiders bite humans only when trapped or crushed against the skin.

Bite marks from most spiders are usually too small to be easily seen. Frequently, the patient will not recall being bitten. Spiders rarely bite more than once, so multiple bites are usually caused by insects such as fleas, bedbugs, ticks, mites, and biting flies. Spider bites often cause minor swelling, redness, pain, and itching. These mild reactions are common and may last from a few hours to a few days. Unfortunately, sometimes more severe reactions to bites or stings can be produced by spider bites. Babies and children may be more affected by bites or stings than adults.

Taxonomically, spiders belong to class Arachnida which is composed by the orders Scorpionida, Acarina, Opiliones, Pseudoscorpiones, and Araneida. These arthropods belong specifically to the last order which is constituted for a large number of families.

Spider bites are usually too small to be easily seen, and often cause minor swelling, redness, pain, and itching.