Snake bites and venom poisoning in the UK: adder bites, first aid and treatment

Envenomation means that venom, a toxin, has been injected by a bite or sting. In the UK the NHS says only 3 types of snake live in the wild: the adder, the grass snake and the smooth snake, and the adder is the only venomous species. Grass snakes are usually green with dark spots down the sides and yellow and black bands around the neck. Smooth snakes are usually grey or brown with a dark pattern that is lighter and less zig-zag than an adder's.

A UK clinical reference article written for doctors notes that snake bites are uncommon in the UK and that the adder is the only indigenous venomous snake, although other species may be kept in private collections or zoos. Of 510 snake bite enquiries to the National Poisons Information Service between 2004 and 2010, adders accounted for 52%, exotic species for 26% and unknown species for 18%.

The Amphibian and Reptile Conservation Trust estimates around 50 to 100 adder bites to people per year in Great Britain, against millions of visits to places where adders live. Adders bite when they are trying to defend themselves, typically when picked up or when a hand or foot is put close to them. Many bites to people occur when the snake is handled.

The conservation charity lists the possible effects of an adder bite, and stresses that not all will be seen in every case and that severity varies substantially. The first symptoms may take from a few minutes to hours to become evident. A UK clinical article says pain is felt immediately at the bite site and that local swelling will follow.

• Severe pain, swelling, redness and bruising at the bite.

• Feeling or being sick, and diarrhoea.

• Itchy lumps on the skin.

• Swelling of the lips, tongue, gums and throat, and difficulty breathing.

• Confusion, dizziness or fainting, and an irregular heartbeat.

• Shock, in more severe cases.

The NHS says the first step is to call 999 or go to A&E. While waiting, the NHS advice is to stay calm, because most snake bites in the UK are not serious; keep the bitten part of the body as still as possible; lie in the recovery position if you can; take paracetamol for pain; try to remember the colour and pattern of the snake or take a photo from a distance if it is safe; and take off jewellery and loosen clothes near the bite in case the skin swells.

The NHS also lists things not to do. Do not go near the snake or try to catch or kill it. Do not try to suck or cut the venom out. Do not tie anything tightly round the bitten part of the body. Do not take aspirin or ibuprofen, because they can make bleeding worse. The conservation charity adds that harming native snakes is illegal and that you should not bring the snake to hospital.

A UK clinical reference for doctors says pre-hospital treatment of an adder bite should consist only of reassurance and immobilisation of the limb, and that a bandage should not be applied because over-tightening has led to complications. If you are outside the UK when bitten, the NHS says to contact the emergency medical services of the country you are in.

The NHS says the bite will be cleaned and bandaged, you may be given an injection to protect against tetanus and you will usually need to stay for at least 24 hours. If the bite was from a venomous snake you are treated with a medicine to fight the toxin, given through a drip.

The clinical reference article explains that staff observe for local swelling for at least two hours, and that a person with no symptoms and no swelling after that may be discharged while all others are admitted for observation. Monitoring includes pulse, blood pressure and breathing, a heart monitor to look for rhythm changes, blood tests including clotting and kidney tests, and ECGs.

The Amphibian and Reptile Conservation Trust says hospitals have access to expert advice, for instance via the National Poisons Information Service, and that treatment has improved substantially in recent decades. It adds that it is increasingly common to treat patients with antivenom, which reduces the severity of symptoms and shortens recovery time, and that adverse reactions to modern antivenoms are uncommon.

In most bites there is little or no envenomation. The charity estimates that in around one third of adder bites the snake does not actually inject any venom, which it calls a dry bite, though there is still a risk of infection and understandable anxiety. Adder bites do not always leave two puncture marks, and the marks can vary from one to three.

Where there is little envenoming, the charity says there is full recovery within a month, although aching and swelling can recur for weeks after the bite. In severe envenoming there may be longer-term effects, but such cases appear to be rare, and rare serious effects can include kidney failure, anaphylaxis, heavy blood loss, coma and cardiac arrest. Children can be more seriously affected than adults, but the charity notes that it is usual for children to recover completely.

The conservation charity advises that, in areas where adders live, people keep to well-used paths or open areas, wear shoes or boots rather than sandals or bare feet, walk slowly and look closely where they are walking, and watch where they put their hands when picking up objects from the ground. Do not try to handle an adder or to shoo one off a path; walk around it leaving plenty of space.

Adders are typically resting underground between November and February, and most sightings are in spring and summer. Children under supervision should be taught not to catch snakes. Dogs are bitten more often when they investigate an adder, so keeping a dog on the lead where adders live reduces the risk.

A snake bite is treated as an emergency, so the route is 999, an ambulance and a hospital emergency department. Follow-up after discharge, such as wound review or advice about persistent swelling, is arranged through the hospital team and your GP.