A snake will sometimes bite in self-defence if disturbed or provoked.
Some snakes are venomous and can inject venom (toxin) as they bite. A bite from a venomous snake is a medical emergency as they can be deadly if not treated quickly.
In the UK, adders are the only venomous snakes found in the wild. People also keep foreign (exotic) venomous snakes, sometimes illegally.
Exotic snakes have been known to bite while being handled carelessly, or when they escape from their cages.
There's also a risk of being bitten while travelling abroad to tropical countries.
Symptoms of snake bites
If an adder injects venom when it bites, it can cause serious symptoms including:
- pain, redness and swelling in the area of the bite
- nausea (feeling sick) and vomiting
- dizziness and fainting
A foreign snake that injects venom when it bites can also cause:
- extensive swelling, blistering and, eventually, gangrene in the area of the bite
- muscle paralysis (an inability to move one or more muscles of the body) leading to difficulties swallowing and breathing
Sometimes, venomous snakes can bite without injecting venom. This is called a ‘dry bite' causing only:
- mild pain (from the snake's teeth puncturing the skin)
Read more about the symptoms of snake bites.
What to do after a snake bite
Immediately after being bitten by a snake you should:
- remain calm and don't panic; snake bites, particularly those that occur in the UK, are not often serious and rarely deadly
- try to remember the shape, size and colour of the snake
- keep the part of your body that has been bitten as still as possible to prevent the venom spreading around your body
- remove jewellery and watches from the bitten limb because they could cut into your skin if the limb swells
- do not attempt to remove any clothing, such as trousers, but loosen clothing if possible
Seek immediate medical assistance by dialling 999 to request an ambulance or visit your nearest accident and emergency (A&E) department.
You should give healthcare professionals a description of the snake to help identify it.
You may be admitted to hospital so the bite can be assessed and your condition closely monitored.
Read more about what to do if bitten by a snake and how snake bites are assessed.
Treating snake bites
In most cases of adder bites, the only treatment required is observation in hospital. As a precaution, you may be asked to stay in hospital for 24 hours to be monitored.
Antivenom medication is an effective antidote to snake venom and can be used to treat more severe snake bites.
In most cases, children bitten by an adder will make a full recovery in about one to two weeks. Adults usually require more than two weeks to recover fully, and a quarter of adults will take between one and nine months.
Read more about how snake bites are treated.
Why do snakes bite?
When a snake bites, it injects venom to immobilise its natural (food) prey. As humans are too large for a snake to eat, snakes bite only in self defence.
Snake bites usually occur when a person accidentally steps on a snake while out walking. However, sometimes people are bitten when they deliberately provoke a snake by striking it or trying to pick it up.
Read more about the causes of snake bites.
Preventing snake bites
Follow the advice listed below if you are in an area where venomous snakes are found.
- look out for warning notices on heaths and commons
- wear boots and long trousers
- never pick up a snake, even if you think it's harmless or it appears dead
- never put your hand in a hole or crevice, for example, between rocks – if you need to retrieve something, stand well back and use a stick to reach it
- if you find yourself very close to a snake, stand completely still – most snakes only strike at moving targets so if you remain calm and still, the snake will escape without harming you
How common are snake bites?
The World Health Organization estimates that around the world there are millions of venomous snake bites each year, resulting in more than 100,000 deaths each year. However, the total number of snake bites and deaths is likely to be even higher than this.
The figures vary widely depending on their source, but the majority of fatalities occur in south and south-east Asia, sub-Saharan Africa, New Guinea and Latin America – especially in rural farming areas of countries, such as India, where access to emergency medical services is limited or non-existent.
About 100 adder bites are reported in the UK each year. Most bites occur between June and August, with the number of bites peaking during in July.
Less than 10 UK residents are bitten by foreign snakes each year, either while travelling abroad or by captive snakes kept in this country.
Where are adders found?
The adder is common throughout mainland Britain and some islands off the west coast of Scotland. They can be found in:
- throughout Wales, including Anglesea
- mainland England
- the Isle of Wight
- Scotland, including some of the Inner Hebridean Islands (a group of islands off the west coast of Scotland)