Idiopathic anaphylaxis: The hidden allergy?

Most people have heard of severe allergies, or anaphylaxis, to food, insect stings, drugs and other common substances, but sometimes no cause at all can be found for a person’s reaction. This condition is called idiopathic anaphylaxis. 

To raise awareness of this little known condition and to help those affected, the Anaphylaxis Campaign has updated its factsheet on Idiopathic anaphylaxis.
Anaphylaxis is the most severe form of allergic reaction and can be fatal in the worst cases, yet is more common than you might think. Food allergy alone is thought to affect 1 – 2% of the adult population and 4-6% of children and there are estimated to be around 30,000 cases of hospitalisation due to anaphylaxis every year. In some cases, these reactions will be termed idiopathic, as even after intense diagnostic investigation, no discernable cause can be found.
Symptoms may begin suddenly and progress quickly, ranging from mild nettle rash, tingling or itchy feeling in the mouth, to severe swelling of the face, throat or mouth, breathing difficulty, severe abdominal pain, nausea, vomiting and in extreme cases there could be a dramatic fall in blood pressure (anaphylactic shock). This causes weakening and floppiness and may cause a sense of impending doom in the patient. Collapse and unconsciousness can follow and reactions of this severity may even prove fatal if not treated promptly with adrenaline.

What is behind Idiopathic anaphylaxis?
This curious and frustrating diagnosis can occur for two main reasons. Firstly, no trigger can be identified because, while an external trigger (such as a food) might be present, tests may fail to pick it up. Secondly however, it could also mean that there is no external trigger at all and the cause is a temporary increase in the reactivity of the body’s immune system.

If an external trigger is present, it may be one of a few possibilities, including:

  • Food – this should be considered a prime suspect, especially foods eaten shortly before the start of an attack
  • Lupin - the seeds from some varieties of lupin are milled to make flour, which is used in baked goods such as pastries, pies, pancakes and in pasta
  • Latex - found in thousands of everyday consumer and healthcare items, with allergy to latex becoming increasingly common over the past 25 years
  • Flour contaminated by mites – this condition is known colloquially as Pancake Syndrome; the medical term is Oral Mite Anaphylaxis, with anaphylaxis occurring shortly after the intake of foods made with mite-contaminated wheat flour
  • Cold induced urticaria/anaphylaxis - in rare cases, anaphylaxis can be caused by chilling. For example, a nine-year-old girl suffered urticaria (hives all over her body) and lost consciousness while swimming in cold water. She was immediately removed from the water and regained consciousness. She had a preceding two-year history of multiple episodes of urticaria while swimming in unheated water (Fernando SL, 2009)

What can be done?

Moira Austin, Helpline Manager for the Anaphylaxis Campaign said; “Our factsheet on Idiopathic anaphylaxis will shine a light for many on their condition, as there is almost nothing out there for patients who receive this diagnosis.  This can be an upsetting, as it provides no closure and means people cannot practice avoidance – one of the key means of managing anaphylaxis – because they simply do not know what they should be avoiding.”
Dr Michael Radcliffe, a member of the Anaphylaxis Campaign’s Clinical and Scientific Panel  who helped to produce the factsheet said: “If allergy-like symptoms are present but the cause is a mystery, it is important that a detailed account is kept, noting time, date, location, consumption and activity in the hours leading up to the reaction. All these details might help to build a picture of the problem and possibly identify a common thread.” 

The Anaphylaxis Campaign is the only UK wide charity to exclusively meet the needs of the growing numbers of people at risk from severe allergic reactions (anaphylaxis) by providing information and support relating to foods and other triggers such as latex, drugs and insect stings.  Their aim is to create a safe environment for all people with allergies by educating the food industry, schools, pre-schools, colleges, health professionals and other key audiences.