England has one native venomous snake, the Adder (Vipera berus). It is the only species of snake in Great Britain capable of delivering venom. Bites are exceedingly rare and almost always occur when the animal is provoked or accidentally stepped upon. Despite the low risk, any bite from an Adder must be treated as a serious medical event that requires immediate professional attention.
Identifying England’s Only Venomous Snake
The Adder is a relatively small and stocky snake, with adults typically measuring between 50 and 65 centimeters in length. The most distinctive feature of the Adder is the dark, continuous zig-zag pattern that runs along the entire length of its back. This marking stands out against the background color, which is usually silvery-grey for males and reddish-brown or copper for females.
The head often features a dark V or X-shaped marking, and the pupils are vertically slit, distinguishing it from the non-venomous Grass Snake and Smooth Snake. Adders prefer habitats that provide both cover and open areas for basking, such as heathland, moorland, rough grassland, and the edges of woodlands. Since they are protected under the Wildlife and Countryside Act 1981, it is illegal to intentionally injure, kill, or sell them.
Understanding the Venom and Bite Risk
The Adder’s venom is primarily hemotoxic, which means it affects the circulatory system and body tissues, causing significant localized symptoms. The immediate effects of a bite often include intense, sharp pain, followed rapidly by swelling, bruising, and inflammation around the wound site. Systemic effects can also occur, including nausea, vomiting, dizziness, and collapse, which can manifest within minutes or be delayed for several hours.
Approximately one-third of all Adder bites are “dry bites,” where no venom is injected, but the wound still requires medical assessment. In the cases where envenomation does occur, about 70% of patients experience only localized effects that are treatable. Fatalities are extremely rare in England; only 14 deaths have been recorded since 1876, with the last occurring in 1975. Bites pose the highest risk to children, the elderly, or those with underlying health issues. Research suggests there are approximately 50 to 100 Adder bites to humans annually across Great Britain.
Encountering Adders: Safety and First Aid
Encounters with Adders are avoidable, as the snakes are shy and only bite if they feel threatened or accidentally disturbed. To prevent an encounter, stay on marked paths in high-risk areas like heathlands and wear sturdy, enclosed footwear for ankle protection. Dog owners should keep their pets on a lead, especially during spring, as dogs are often bitten when investigating basking snakes. If an Adder is spotted, leave it alone and give it a wide berth, allowing it to move away naturally without provocation.
First Aid for Adder Bites
If a bite does occur, the immediate action is to remain calm, as panic can increase the spread of any injected venom. The affected limb should be kept as still as possible and positioned below heart level to slow the movement of venom.
It is imperative to seek urgent medical attention by calling 999 or going to a hospital emergency department immediately. While waiting for help, remove any jewelry or restrictive clothing near the bite site in case swelling occurs. Never attempt to cut the wound, suck out the venom, apply a tourniquet, or use a “snake bite kit,” as these actions are ineffective and can cause further damage or infection.