Snake venom can affect every major organ system in the body directly or indirectly. The venom of rattlesnakes and other pit vipers damages tissue around the bite, produces changes in blood cells, prevents blood from clotting, and damages blood vessels, causing them to leak. These changes can lead to internal bleeding and heart, respiratory, and kidney failure. The venom of coral snakes affects nervous system activity but causes little damage to tissue around the bite. The symptoms of pit viper poisoning vary widely, depending on the size and species of snake, the amount and toxicity of the venom injected, the bite's location, the victim's age and size, and the presence of other medical problems.
Most bites occur on the hand or foot.
These symptoms are rarely delayed more than 20 to 30 minutes. The pain can vary from mild to severe. A poisonous bite can be diagnosed on the basis of fang marks, redness, pain, swelling, and tingling and numbness in the fingers or toes or around the mouth, among other symptoms. A metallic or rubbery taste in the mouth has been noted after bites by some species of rattlesnakes. If untreated, the swelling can progress, affecting the entire leg or arm within several hours.