What causes anaphylaxis?

What causes anaphylaxis?

The things that cause anaphylaxis are not usually thought of as dangerous. The most common causes of anaphylaxis are food and venom (wasp or bee stings), however anaphylaxis can also occur after exercise.

Your GP or nurse should have spoken to you about what your triggers are so you can avoid them. Foods are the most common trigger in children, teens and young adults. Insect stings and medications are relatively common triggers in middle-aged and older adults. 3


Anaphylaxis is highly likely when any one of the following three criteria is fulfilled. 3

1. Acute onset of an illness (minutes to several hours) with involvement of the skin, mucosal tissue, or both (eg, generalized rash, itching, or flushing, swollen lips-tongue-uvula)

And at least one of the following:

A) Respiratory compromise e.g. dyspnoea (shortness of breath), wheeze-bronchospasm, stridor (high-pitched breath sound), reduced peak expiratory flow, hypoxaemia (low blood oxygen level))

B) Reduced blood pressure or associated symptoms of end-organ dysfunction (eg. hypotonia [collapse], syncope [dizziness], incontinence) or

Common triggers of anaphylaxis include…

2. Two or more of the following that occur rapidly after exposure to a likely allergen or other trigger for that patient (minutes to several hours)

A) Involvement of the skin-mucosal tissue (e.g. generalized rash, itch-flush, swollen lips-tongue-uvula)

B) Respiratory compromise (e.g. dyspnoea, wheeze-bronchospasm, stridor, reduced peak expiratory flow, hypoxaemia)

C) Reduced blood pressure or associated symptoms (e.g. hypotonia [collapse], syncope, incontinence)

D) Persistent gastrointestinal symptoms (e.g. crampy abdominal pain, vomiting) or

3. Reduced blood pressure after exposure to known allergen (for example, after an insect sting, reduced blood pressure might be the only manifestation of anaphylaxis; for that patient (minutes to several hours)

A) Infants and children: low systolic blood pressure (age-specific) or greater than 30% decrease in systolic blood pressure

B) Adults: systolic blood pressure of less than 90 mm Hg or greater than 30% decrease from that person’s baseline PEF.

Sometimes the triggers for anaphylaxis may be unknown.

3. J Allergy Clin Immunol Volume 127, Number 3

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