Spiders produce venom in glands which are consistent with the chelicerae (= scissors) and injected in conjunction with bite. The poison is generally used to paralyze prey. Native spiders penetrate human skin with their bite is not usually.
They can be found in our gardens, the bananas that are often imported have tarantulas in the crates fortunately tarantulas are not dangerous to humans. However the infection that can arise from a bite is. The black widow spider (Latrodectus MatAns – Southern Italy), however, can cause poisoning/ life threatening symptoms/ reactions.
They can be found in Asia, America and Africa. Latrodectus species contain a protein (alpha-latrotoxin) with which takes specific action against nerve endings. This set acetylcholine , norepinephrine including transmitter release explosively, and may cause pain at first, then muscle rigidity and many other scary symptoms. Death by their bites have been reported. Loxosceles (North America) and produce hemolytic dermatonekrotische toxins which cause ulcers.
Bacterial infections caused by spider bites can be treated in the hospital with antibiotics and anti-inflammatory.
For exotic spiders (Letrodectus species), which like to be kept in a terrarium, there are specific antisera for the bites.
For humans, the domestic spider is harmless, since they generally can not penetrate the skin.