Yearly, about 200 patients are treated at hospitals in Sweden after bites from the adder, Vipera berus, the only domestic venomous snake in Sweden. Moderate or serious symptoms occur in 20-30% of those patients. Sometimes no symptoms occur, which depends on if the snake has injected venom or not.
Adder bites often results in severe local pain and progressive swelling and a bluish discoloration. In serious cases early general symptoms might include dizziness, nausea, vomiting, diarrhea, abdominal pain, difficulty breathing, hypotension, cardiac disturbances, impaired consciousness.