The extent of tissue necrosis varies from person to person, depending on body size and general health and other factors, including the amount of venom injected, the area involved and the number of previous bites. It is difficult to predict which bites will progress to ulceration. Fortunately, the vast majority of bites are trivial, go unnoticed and heal spontaneously. Most patients seek medical attention late, by which time the pathologic necrotic process has already begun. Statistically, most bites are on the lower extremity and buttocks.
First category is the most prevalent.
At this stage, little venom is injected and the bite is not noticed by the patient or reported to a doctor. Second category is characterized by a local cytotoxic reaction. Mild to severe pain usually develops 2-8 hours after the initial bite. Within 3-4 days necrosis develops and a dark eschar develops which gradually hardens. By the 7-14 day the wound edges become uneven and the center of the wound sinks and the eschar sloughs, leaving a painful ulcer.