A primary concern of the bite of a<unk>  is the effect of its venom. A<unk>  envenomation occurs whenever a<unk>  injects venom into the skin. Not all<unk> s involve injection of venom, and the amount of venom injected can vary based on the type of<unk>  and the circumstances of the encounter. The mechanical injury from a<unk>  is not a serious concern for humans. However, it is generally the toxicity of<unk>  venom that poses the most risk to human beings; several<unk> s are known to have venom that can cause injury to humans in the amounts that a<unk>  could inject when biting. While venoms are by definition toxic substances, most<unk> s do not have venom that is directly toxic (in the quantities delivered) to require medical attention and, of those that do, severity is typically mild.<unk>  venoms work on one of two fundamental principles; they are either neurotoxic (attacking the nervous system) or necrotic (attacking tissues surrounding the bite). In some cases, the venom affects vital organs and systems. The venoms of the widow<unk> s, Brazilian wandering<unk>  and Australian funnel-web are neurotoxic. Heart muscle damage is an unusual complication of widow venom that may lead to death. Pulmonary edema, which is fluid accumulation in the lungs, is a feared and potentially serious but uncommon complication of funnel-web venom. Recluse and South African sand<unk>  venoms are necrotic. Recluse venom may also cause severe hemolysis (destruction of red blood cells), though this is typically uncommon.
Spider bite
Dog bite
Cat bite
Animal bite
Centipede bite
Nail biting
Snakebite
Needlestick injury