Symptoms of snake bites

Venomous snakes can sometimes bite without injecting venom. This is called a "dry bite", and it causes mild pain from the snake's teeth puncturing the skin as well as anxiety .

If there are no other symptoms, such as swelling, it's probably a dry bite.

You should still visit your nearest accident and emergency (A&E) department  as signs that venom has been injected might not appear until later  up to two hours or more after an adder bite, or even longer after an exotic snake bite.

Venomous snake bites (adder and foreign)

Adder and foreign snake bites can cause similar symptoms.

Symptoms of an adder bite when venom has been injected include:

• severe pain at the location of the bite
• swelling, redness and bruising at the location of the bite, spreading up the bitten limb
• feeling sick (nausea) followed by vomiting
• diarrhoea
• itchy lumps on the skin ( hives or nettle rash)
• swelling of the lips, tongue and gums
• breathing difficulties with wheezing, similar to asthma
• mental confusion, dizziness or  fainting  
• an irregular heartbeat

For foreign snake bites, symptoms may also include:

• dizziness, mental confusion, faintness, collapse and shock
• bleeding from the mouth, nose and wounds
• vomiting blood or passing  blood in urine or stools
• muscle paralysis , which can lead to breathing difficulties

In the most severe cases, a venomous snake bite may cause:

• extensive swelling, blistering and eventually tissue death (gangrene) in the area of the bite
• paralysis  starting with drooping of the upper eyelids and progressing down the body to produce an inability to swallow, breathe or move
• shock  and loss of consciousness
• kidney failure  with little or no urine being passed
• massive blood loss  as a result of bleeding from the mouth, nose and wounds, vomiting blood, and passing blood in urine or stools
• death

Dial 999 to ask for an ambulance if someone is bitten by an adder or foreign snake and faints or develops symptoms of  anaphylaxis .

Anaphylaxis

In a small number of people, a snake bite can trigger a severe allergic reaction, known as anaphylaxis or anaphylactic shock. This can occur immediately after a bite or several hours later.

Anaphylaxis should always be treated as a medical emergency. Left untreated, anaphylaxis can be life threatening.

Symptoms of anaphylaxis include:

• itchy skin with hives and redness
• swollen face, lips, tongue and throat
• swelling in the throat that can cause breathing difficulties
• wheezing and difficulty breathing 
• rapid heartbeat
• nausea, vomiting and diarrhoea

Anaphylaxis can also cause a drop in blood pressure, which can lead to shock and cause symptoms such as:

• dizziness or mental confusion
• faintness, loss of consciousness or collapsing 
• cold and clammy skin
• blindness

Read more about  anaphylaxis .

Shock

Someone who's been bitten by a snake may go into shock. Shock is a life-threatening condition that occurs when there's an insufficient supply of oxygen to the body.

Shock should always be treated as a medical emergency  you should dial 999 to request an ambulance immediately.

Symptoms of shock include:

• faintness or collapsing
• pale, cold, clammy skin
• sweating 
• rapid, shallow breathing
• weakness and dizziness
• blindness
• feeling sick and possibly vomiting
• drowsiness or loss of consciousness

After calling an ambulance, lay the person down and raise and support their legs. Use a coat or blanket to keep them warm.

This is so staff can keep you under observation in case you develop symptoms that suggest venom has been injected.

As a precaution, you may be asked to stay in hospital for at least 24 hours so your blood pressure and general health can be monitored.

Antivenoms

Antivenoms are antidotes to snake venom and are used to treat more severe snake bites. They contain antibodies, which are proteins that neutralise the effects of the snake's venom toxins.

In some people, antivenoms can trigger a severe reaction called anaphylaxis, so it's important you're closely monitored after receiving this treatment. Anaphylaxis is treated with adrenaline.

Because of the risk of anaphylaxis, antivenom should only be given by a qualified healthcare professional.

If the snake bite is severe and your blood pressure has fallen significantly, you may need intravenous fluids administered directly into a vein in your arm. You may also need a blood transfusion  if you've lost a lot of blood.

Recovery

Recovery times for snake bites can vary depending on the species of snake involved.

In most cases, children bitten by an adder will make a full recovery in one to two weeks.

Adults usually take more than three weeks to recover fully, with a quarter taking between one to nine months. Early treatment with antivenom can reduce these times.

During the recovery period, you may experience episodes of pain and swelling in the area that's been bitten.

These symptoms can usually be controlled by taking over-the-counter painkillers, such as paracetamol , and continuing to exercise the limb.