Antivenom is a type of serum used in treatment of poisonous snake and insect bites. Antivenom is largely species specific, although some will work with more than one species.
Antivenom is created by taking the venom or toxin from the animal, diluting it, and injecting it into a horse, sheep, or goat. The animal will create antibodies to the toxin which can then be harvested from the blood of the animal.
Most types of antivenom can be freeze-dried and, as such, can be stored for long periods of time at room temperature. However, some must remain in liquid form and require constant refrigeration.
In most cases, although antivenom will neutralize venom, it will not reverse damage already done. As such, it must be administered as quickly as possible to be the most effective. However, both immediate anaphylactic shock and slower allergic reactions are common.