Cytotoxic Venoms
This is a milder venom that generally causes only localized symptoms at the location of the bite. This is a cell destroying venom that destroys everything in it's path - blood vessels, cells and tissues. The symptoms of the invasion of this venom are generally seen around 10-15 minutes after the snake encounter. The results are generally localized pain accompanied by severe swelling and bleeding. One can easily spot the formation of red blisters near the bite area. This venom causes blue/black spotting due to limited blood circulation. The body often revolts against the invasion of this venom by causing nausea and vomiting. If this venom is not treated within four hours, it generally needs an amputation. Puff adders (bitis arietans) are the snakes to be avoided if one is pain phobic.
Myotoxic Venoms
This venom is found in the 'bothrops moojeni' snakes, commonly known as the Brazillian lancehead snakes. This venom is known to cause muscular necrosis. Its symptoms are a thickened-tongue sensation, dry throat, thirst, muscular spasms and convulsions. It also causes the stiffness of the jaw, neck, trunk and limbs along with severe pain in movement. The victims often start with drooping eyelids and then turn to more austere results like loss of breath and blackish brown urine discharge. Myotoxic venom contains peptides that destroy the muscle fiber proteins and result in myonecrosis (muscle destruction). In the very later stages (when treatment is delayed) of the spread of this venom, the muscle proteins enter the blood stream. The kidney overworks in trying to filter out this junk and often gives up trying. This kidney failure is the reason for the dark coloration of urine.
When dealing with the effect of spider venom on humans there are two types. Some spider venom is neurotoxic; that is, it affects the human nervous system beyond the site of the bite. The black widow venom is neurotoxic. A principal component of this venom is a-latrotoxin. A black widow bite causes rigidity , cramp, and paralysis of the sympathetic systems. Occasionally it causes death.
Other spider venom is necrotic and causes damage to the tissues surrounding the site of the bite. The recluse spiders have necrotic venom. The damage usually results in skin blisters, ulcers and blackening of the local tissues.