No; there are two main types of spider venom: necrotic and neurotoxic. Neurotoxic venom affects the nerves. A bite from a black widow can cause muscle cramps, spasms, numbness, tingling, or even total loss of feeling in a limb or area of the body. Neurotoxic venom can affect multiple areas of the body. Necrotic venom, including the venom of brown recluse spiders, destroys living tissue. It forms purple or black discoloration that looks like a bruise. Underneath the surface, the venom will form an ulcer that can grow worse if the affected area is not treated.