Is it Anaphylaxis?

With the increased prevalence and awareness of Allergies, an increasing number of patients will be presenting to their emergency doctors with what looks like anaphylaxis. The emergency doctor knows that he / she could be dealing with a life-threatening situation and has to make quick decisions. Often Adrenaline is given at the time, and the patient is then left with the fear of this situation recurring.

It is therefore very important for the diagnosis of Anaphylaxis not to be taken lightly, both for the immediate management of the patient and the long-term implications.

It is also more likely that an atopic patient who has had 1 anaphylactic reaction will develop "benign" acute urticaria (hives), from eating strawberries say, and will panic and develop "difficulty breathing" due to hyperventilation. At 1am when this patient presents to an unknown doctor, it would be difficult to withhold adrenaline. This is one reason why a good history and objectivity should prevail. Then there are the patients who have never had a true anaphylactic reaction, but have had several episodes or recurrent acute generalised urticaria with angioedema (swelling) of the face associated with several subjective symptoms that make the diagnosis of anaphylaxis possible. Oftentimes these patients are labelled as "Anaphylactic" and given an Epi-pen. It then becomes very difficult to remove that label and the associated fear.

Anaphylaxis means a severe, potentially life-threatening allergy. No universally accepted definition exists, because anaphylaxis comprises a constellation of features.

The features of anaphylaxis include:

  • Urticaria (hives)
  • Erythema (generalised redness) or Flushing
  • Pruritus (generalised itching) without a "rash"
  • Angioedema (swelling)
  • Laryngeal oedema
  • Asthma
  • Rhinitis
  • Conjunctivitis
  • Itching of the palate or ear canal
  • Nausea, vomiting, abdominal pain
  • Palpitations or "fluttering in chest"
  • Sense of impending doom
  • Fainting, light-headedness
  • Collapse
  • Loss of consciousness
  • Convulsion ("fits")

A good working definition is that 'anaphylaxis should involve one or both of two severe features: respiratory difficulty (which may be laryngeal oedema or asthma) and hypotension (which can present as fainting, collapse or loss of consciousness)'

Confusion with the definition arises because systemic allergic reactions can be mild, moderate, or severe. Using the strict definition above, someone who has generalised urticaria, angioedema and nausea would not be described as anaphylactic, as neither respiratory difficulty nor hypotension, the life-threatening feature, is present.

The onset and course of anaphylaxis can vary among patients. The features that are taken most seriously are laryngeal oedema and cardiovascular collapse, as these are the most frequent causes of death.

Urticaria and angioedema have been reported to occur in about 88% of anaphylactic reactions (clearly the most common manifestation). Flushing was noted in 46% and pruritus without a "rash" in 5%. There is almost always some skin manifestation in anaphylaxis and some would even say the diagnosis should be seriously doubted if the skin is not involved. One should also remember that some of the most severe anaphylactic reactions do not have noticeable skin reactions. Hugh Sampson reported skin involvement in only one of six food-induced deaths occurring in children, and he states: "Anaphylaxis should never be ruled out on the basis of absent skin symptoms."

It is because of these difficulties surrounding the diagnosis of Anaphylaxis that prompted me to draft a letter, which I will give to all these cases of "? Anaphylaxis", to carry with them so if they have an attack they present the letter to the attending doctor or nurse to fill out, preferably before adrenaline is given. The drafted letter is as follows:

(Anyone with an uncertain diagnosis of Anaphylaxis might feel free to download and copy this letter which is an Adobe Acrobat PDF. If you don't have the free Adobe Acrobat Reader software you can download it by clicking here.)

Useful Anaphylaxis Links:

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