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Anaphylaxis is a severe and potentially life-threatening reaction to a trigger such as an allergy. It can occur within seconds or minutes of exposure to something you’re allergic to, such as peanuts or bee stings. Common anaphylaxis triggers include certain foods, some medications, insect venom and latex.

Anaphylaxis brought on by food, medication, insect venom, or drugs

What causes anaphylaxis?

Anaphylaxis is the result of the immune system, the body’s natural defence system, overreacting to a trigger. This shock can sometimes cause your blood pressure to suddenly drop or your airways to narrow. This is often caused by something you’re allergic to, but not always. Common anaphylaxis triggers include:

  • foods – including nuts, milk, fish, shellfish, eggs and some fruits
  • medicines – including some antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) like aspirin
  • insect venom – particularly wasp and bee stings
  • general anaesthetic or contrast agents – dyes used in some medical tests to help certain areas of your body show up better on scans
  • latex – a type of rubber found in some rubber gloves and condoms

How can it be diagnosed?

Anaphylaxis symptoms usually occur between minutes of exposure to an allergen, or half-hour or longer after exposure and symptoms can include a rapid, weak pulse; a skin rash; or nausea and vomiting.

There are two main types of reaction which could occur:

Uniphasic – these come on quickly and symptoms get rapidly worse, but once treated, the symptoms go and don’t return.

Bi-phasic – these are reactions which may be mild or severe to start with, followed by a period of time when there are no symptoms, and then increasing symptoms with breathing and blood-pressure problems.

The results of skin prick tests and blood tests can help the specialist identify the cause of the problem.

What are the risks?

There aren’t many known risk factors for anaphylaxis, but some things that might increase your risk include:

  • Previous anaphylaxis. If you’ve had anaphylaxis once, your risk of having this serious reaction can increase with more severe symptoms.
  • Allergies or asthma. People who have either condition are at increased risk of having anaphylaxis.
  • Certain other conditions. These include heart disease and an abnormal accumulation of a certain type of white blood cell (mastocytosis).

Treatment options available

Anaphylaxis can require an injection of epinephrine (sometimes referred to as ‘pens’) containing epinephrine (known as adrenaline) which can be prescribed for people at risk.

If you experience attacks fairly frequently, your doctor may prescribe an oral steroid or oral antihistamine to help manage your condition. 

Idiopathic (spontaneous) anaphylaxis

What is idiopathic anaphylaxis?

Idiopathic anaphylaxis is when a patient experiences anaphylaxis, however no trigger can be identified.

How is it diagnosed?

Some GPs have a clear understanding of allergies and similar conditions, but your doctor may need to refer you to an allergy clinic for diagnosis. The results of skin prick tests and blood tests can help the specialist identify the cause of the problem.

If no cause can be found then the term idiopathic anaphylaxis is used.

Can it be managed and treated?

Cases in which attacks are occurring frequently may require a few weeks or months of regular treatment such as a daily oral steroid to prevent further attacks and help the condition to settle down.

Exertion-induced anaphylaxis

What is exertion-induced anaphylaxis?

Exercise-induced anaphylaxis is an uncommon, potentially-serious condition in which anaphylaxis occurs during or after physical activity. 

What are the risks?

In severe cases, there is risk of a dramatic fall in blood pressure (anaphylactic shock). The person may become weak and floppy and may have a sense of something terrible happening. This can lead to collapse and unconsciousness.

Can it be managed and treated?

It is advised to use prescribed adrenaline as soon as a severe reaction is suspected to be occurring. If you are unsure what triggers your allergy, it is preferable not to exercise alone

Anaphylaxis in mastocytosis

What is anaphylaxis in mastocytosis?

Mastocytosis is a rare disease of the skin in where mast cells gather in body tissues, such as the skin, internal organs and bones. When mast cells detect a substance that triggers an allergic reaction (an allergen), they release histamine and other chemicals into the bloodstream which can cause mild to life threatening reactions. 

How is it diagnosed?

The following tests are commonly used to look for signs of mastocytosis:

  • Skin tests – Your GP or skin specialist (dermatologist) may rub the affected areas of skin to see if it becomes red, inflamed and itchy. This is known as Darier’s sign.
  • Blood tests – including a full blood count (FBC) and measuring blood tryptase levels
  • Ultrasound – an ultrasound scan to look for enlargement of the liver and spleen if it seems likely a DEXA scan to measure bone density
  • A bone marrow biopsy test – where a local anaesthetic is used and a long needle is inserted through the skin into the bone underneath, usually in the pelvis

What are the risks?

If you have systemic mastocytosis or extensive cutaneous mastocytosis, your risk of a severe allergic reaction (anaphylaxis) is increased.

Can it be managed and treated?

There’s no proven cure for mastocytosis, so it is advised to stay away from the things that trigger your symptoms. Other treatments used to try to relieve the symptoms include:

  • Antihistamines – used to treat the symptoms of red skin and itchiness
  • Steroid cream – used to treat mild to moderate cases of cutaneous mastocytosis