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Snakes sometimes bite in self-defence if they are disturbed or provoked. Adders, or vipers, are the only wild venomous snakes in the UK. The adder is the only venomous snake that is found naturally in the wild in the UK.
This article focuses on the bites of adders. See the Health topic about Snake bites (foreign) for more information about other types of snake bites.
Adders are found in:
Adders sometimes bite without injecting any venom (toxins produced by the snake). This is called a ‘dry’ bite and may cause:
If an adder injects venom when it bites it can cause more serious symptoms including:
See Snake bites, adder - symptoms for more information.
How common are snake bites?
In the UK, the adder is the only venomous snake that is found naturally in the wild. See Snake bites, adder - causes for more information about adders.
Each year, approximately 100 cases of adder bites are reported in the UK. Most bites occur between February and October, with the number of bites peaking during the summer months.
Worldwide, there are around 5 million snake bites every year.
Although adder bites can be painful, they are rarely serious. About 7 out of 10 adder bites only result in pain and swelling in the area that was bitten. Since records began in 1876 there have only been 14 reported deaths caused by adder bites, with the last death occurring in 1975.
Severe cases of adder bites are unusual, but they can be treated effectively in hospital using anti-venom medicine. See Snake bites, adder - treatment for more information.^^ Back to top
There are two different types of snake bite:
The effects of venomous bites may be more severe in children, because they are smaller.
Symptoms of dry bites
The symptoms of a dry bite are:
If there are no other symptoms, such as swelling, it is probably a dry bite.
Although dry bites require no medical treatment, if you are bitten by a snake you should visit your local accident and emergency (A&E) department. This is because signs that venom has been injected might not appear until later, up to two hours or more after the bite.
Symptoms of venomous bites
The symptoms of a venomous snake bite include:
Dial 999 to request an ambulance if someone who is bitten by an adder faints or develops any other symptoms that may indicate anaphylaxis.
Anaphylaxis (severe allergic reaction)
Symptoms of anaphylaxis include:
Anaphylaxis can also cause a drop in blood pressure, which can lead to shock and cause symptoms of:
Anaphylaxis should always be treated as a medical emergency, regardless of how severe it seems. Left untreated, the most serious cases of anaphylaxis can be life-threatening.
See the Health topic about Anaphylaxis for more information.
What should I do if I am bitten by an adder?
If you are bitten by an adder you should visit your nearest accident and emergency (A&E) department, even if your symptoms are only mild. Hospital staff will be able to check for any signs that venom has been injected through the bite.
You can use the local services search to find your nearest A&E department.
Adder venom contains two kinds of toxins (poisons) which are designed to immobilise or kill the snakes prey:
Haemotoxins can cause a drop in blood pressure, and prevent blood from clotting, which causes bleeding. This may result in:
Cytotoxins cause blood and plasma (the liquid part of blood that contains antibodies and other proteins) to leak into the tissue near to the bite. This can damage and kill tissue cells and result in the affected tissue:
Why do snakes bite?
As humans are far too large for a venomous snake to eat, nearly all snake bites occur when somebody provokes a snake into acting in self-defence.
In many cases, provocation occurs by accident, for example, when a person accidentally steps on a snake while out walking. However, sometimes snake bites occur when someone deliberately provokes a snake by:
Where adders live
You can find adders in:
Adders are not found in Ireland or in the:
The adder is common throughout mainland Britain and some of the islands off the west coast of Scotland. It is not found in Ireland. Adders are the only snakes in Scotland.
Appearance of adders:
Adders can be confused with:
Adders are not aggressive snakes and they will usually only bite if they are disturbed. Most adder bites occur when someone accidentally steps on an adder or tries to pick one up.^^ Back to top
If you have been bitten by an adder or an unidentified wild snake in the UK, you should seek immediate medical attention (see Snake bites, adder - treatment).
The healthcare professionals who treat you may ask about the colour and size of the snake to identify which type of snake has bitten you.
You may be admitted to hospital, where the severity of a snake bite can be assessed by:
In more serious cases of snake bite, an electrocardiogram (ECG) may be used to monitor your heart function.
An ECG records the rhythms and electrical activity of your heart. A number of electrodes (small, sticky patches) are placed on your arms, legs and chest. The electrodes are connected to a machine that records the electrical signals of each heartbeat.^^ Back to top
There are a number of misconceptions about what to do immediately after a snake bite. In order to clear up these misconceptions, this section will provide advice about what to do and what not to do in the event of a snake bite. If you or someone else has been bitten by a snake, you should follow the advice outlined below and seek medical attention by visiting the nearest accident and emergency (A&E) department or dialling 999 to request an ambulance if it is a medical emergency.
If you or someone else is bitten by a snake you should follow the advice listed below.
If you or someone else is bitten by a snake you should never:
Seeking medical attention
If you are bitten by an adder in the UK, you should visit your nearest accident and emergency (A&E) department. You can find the closest A&E department by using the Local Services search.
In most cases of adder bites, the only required treatment is observation in hospital, in case any symptoms develop that suggest venom has been injected.
You may be asked to stay in hospital for at least 24 hours as a precaution, so that your blood pressure and general health can be monitored.
In more severe cases of adder bites, an effective antidote to snake venom (anti-venom medication) can be used.
Anti-venoms are produced by injecting a small, non life-threatening amount of snake venom into a large animal, usually a horse. The animal's immune system (natural defence system) produces antibodies. These are proteins that stick onto toxins and are capable of neutralising their effects. The antibodies are then taken from the animal, purified and stores in a refrigerator until they are needed.
In some people, anti-venoms can trigger a severe allergic reaction called anaphylaxis, so it is important that you are closely monitored after receiving your first dose. If you experience anaphylactic symptoms, such as an itchy rash, a fall in blood pressure or breathing difficulties this can be treated with adrenaline. See the Health topic about Anaphylaxis - treatment for more information.
Due to the risk of anaphylaxis, anti-venoms should only ever be administered by a qualified health professional.
In snake bite cases where there has been a significant fall in blood pressure, you may also need fluids given through a drip into your arm.
In cases of adder bites, most children will make a full recovery in about 1-3 weeks. Adults usually require more than three weeks to recover fully, and a quarter of adults will take between 1-9 months.
During the recovery period, you may experience episodes of swelling and pain in the area of the body that has been bitten. These symptoms can usually be controlled by taking the over-the-counter painkillers such as paracetamol. Always read the manufacturer’s instructions to make sure that:
After an adder bite, a person may go into shock. Shock is a life-threatening condition that occurs when there is an insufficient supply of oxygen to the body.
Shock should be treated as a medical emergency and you should dial 999 to request an ambulance immediately.
Symptoms of shock include:
After calling for an ambulance, you should lie the person down and raise and support their legs. Use a coat or blanket to keep them warm. See First aid for shock for more information and advice.^^ Back to top
If you are travelling in parts of the country and at times of the year when adders are around, the advice outlined below will help to prevent you being bitten.
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