Causes of Anaphylaxis:

The causes of anaphylaxis include:

• Foods and food additives
  Those most often involved are nuts and seeds, fish, shellfish, egg, milk, soya and wheat.  These foods account for over 90% of cases in which foods are found to be involved.  A number of other foods are occasionally found to cause anaphylaxis, including some fruits and vegetables and certain spices.  When anaphylaxis has no clear cause, it is often wondered whether food additives, for example sulphites, may be responsible.  However, although this explanation is sometimes suspected, it is not often proven.
  When a particular food is the cause of anaphylaxis, symptoms usually begin 5-30 minutes after ingestion, but occasionally 1-2 hours after.  Any food eaten earlier than this is unlikely to be the cause.  Even so, patients will very commonly suspect a particular food or foods, even when the interval has been far longer.  Although it is very important indeed that foods that have previously caused anaphylaxis should be excluded, the avoidance of a range of foods that have no connection with the problem will inevitably make things difficult in future.  For this reason it is important that such patients have appropriate investigations carried out at an allergy clinic.
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• Drugs
  A wide range of drugs, and especially penicillins, similar antibiotics, anaesthetic drugs, intravenous infusion solutions, radio-opaque dyes used for X-rays, and the group of painkillers called NSAIDs (non-steroidal anti-inflammatory drugs), can occasionally cause anaphylaxis.  Any drug taken within an hour of an attack of anaphylaxis attack should be carefully noted.  Drugs called beta-blockers, used for heart disease or high blood pressure, can change mild reactions from another cause into severe anaphylaxis because they block part of the natural defence against anaphylaxis.  Heart or blood-pressure drugs called ACE-inhibitors are commonly associated with angioedema, although if anyone suffering anaphylaxis is taking such a drug it should be switched to an alternative.  Not infrequently, attacks may stop once this change is made
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• Rubber Latex
  The natural latex, the main raw ingredient of rubber, is present in rubber gloves, balloons, elastic, many medical products, and in many things encountered in daily life. Sufferers are nearly often health care workers, mainly nurses, or have other occupational contact with latex. They may get anaphylaxis from bananas, avocados, kiwi fruit, figs, or other fruits and vegetables including even potatoes and tomatoes.
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• Bee or wasp stings
  Allergic reactions to bee and wasp stings are not uncommon, although the severe form is, thankfully, rare.  Allergy is thought to be the explanation when when a sting causes faintness or collapse, a difficulty in breathing caused by wheeze or throat swelling, a generalised rash or a swelling in a part of the body which has not been stung.  A large swelling (even up to the size of a plate) in the part of your body which was stung is not a sign of allergy.  It is not true that if you have had one allergic reaction to a bee or wasp, that the next is certain to be more severe.  It quite likely that it will be the same and just as likely that no allergic reaction will occur.  In only one case in ten will it be more severe.
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• Exercise
  Exercise may precipitate anaphylaxis in some people.  In other, the exercise may need to follow food for anaphylaxis to occur.  Whilst it does appear that in some cases it does not matter what the food is, in other cases investigation shows that a particular food is involved.

• Food-dependent exercise-induced anaphylaxis
  This type of reaction occurs during or after exercise and only when a particular food was eaten within the hour or two previously.  As it is usual that the same food eaten without exercise causes no symptoms, then the relationship is not normally noted by the patient.  Similarly in such cases, any amount of exercise can be taken without any problem if the culprit food has not just been eaten.  A relatively limited group of foods has been blamed as capable of causing this rare condition.  The commonest identified cause is wheat, and normally a skin-prick test will show this.  Other foods that have been blamed include celery, shrimp/prawn, apple, squid, abalone, hazelnut, grape, egg, orange, cabbage and chicken.

• Unknown
  At least one third of all sufferers of anaphylaxis have attacks that are completely unexplained by an allergy.  No cause can be found despite all investigations.  Doctors call such unexplained attacks idiopathic anaphylaxis.  Idiopathic means quite simply that the cause is unknown.  Very thorough studies have been made of groups of patients suffering from idiopathic anaphylaxis to see how worthwhile it might be to take allergy investigations further in such patients.  However, when such thorough studies are done, in extremely few cases is a previously missed allergic cause uncovered.  Experts believe that these cases have a disorder of the certain cells of the immune system and that this abnormality makes them trigger-happy.  Sufferers may be interested to read an excellent short book about the condition idiopathic anaphylaxis (see below). 

• Wrong diagnosis
  A proportion (about 10%) of people sent to specialists with a diagnosis of anaphylaxis have a mistaken diagnosis and have not had anaphylaxis.  It is obviously essential to clarify the correct diagnosis for such patients as they may be spared unnecessary fear and wrong treatment.

Further Reading: