Snake Envenomation (Adder Bite)

Snake envenomation in the UK typically involves the adder, the only native venomous snake. When a dog or cat is bitten, venom is injected under the skin, triggering a cascade of local and sometimes systemic effects. The severity can range from mild swelling at the bite site to more widespread reactions affecting circulation, clotting, or other organ systems. Owners often notice sudden pain or distress during a walk in heath, moorland, or woodland, followed by swelling that may appear within minutes to hours. The bite site itself can be difficult to see beneath fur, and the degree of swelling or bruising varies. Some animals show only local signs, while others may develop vomiting, collapse, or lethargy. This page explores the signals that may prompt concern, the mechanisms by which adder venom affects the body, the investigations used to assess severity and guide decisions, and the range of approaches taken in different cases. Each animal's response to envenomation is individual, shaped by factors including the volume of venom delivered, the site of the bite, and the animal's size and health.