GP Guide to Anaphylaxis, Food Allergy and Food Intolerance
The following is intended as a guide to the non-specialist management of anaphylaxis, food
allergy and food intolerance. If the patient’s case falls outside of the stated criteria then a
referral to the Peninsula Specialist Immunology and Allergy Service may be necessary for
further assessment.
Anaphylaxis
Current NICE guidelines recommend that any patient who has experienced anaphylaxis to
an unknown trigger should be referred to a specialist centre. If the causative trigger (eg a
specific food) has been identified, referral may not be required as long as the patient has a
clear emergency plan for future symptoms, as follows;
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Avoid specific identified trigger
Education on symptom recognition in case of accidental exposure
Knows to call 999 and use keyword ‘Anaphylaxis’ if develops severe allergic
symptoms (difficulty breathing, dizziness)
Self-injectable adrenaline (2 devices to be carried at all times) for use against
anaphylactic symptoms (airway or cardiovascular compromise) if trigger
unavoidable, ie not for drug reactions.
Supply of long acting non-sedating antihistamines (eg, cetirizine 10mg)
If anaphylaxis occurred to an identified drug trigger, primary and secondary care records
should be updated with this information and the patient advised to wear a medical alert
bracelet. A home supply of self-injectable adrenaline in this context is not required.
If risk of subsequent anaphylaxis, and particularly if prescribing self -injectable adrenaline,
ensure the patient is not on a non-cardioselective beta-blocker and that cardio-selective
beta-blockers are changed to alternative medications if possible. Asthma care should be
optimised. Any patient with a tendency to angioedema should avoid ACE-I.
Food Allergy
It is important to differentiate between food allergy and food intolerance.
Food allergy can develop at any age although is more common in children and it can
develop to any food, although some foods are more allergenic than others. Food allergy is
characterised by a Type 1 Hypersensitivity reaction and therefore symptoms are rapid in
onset and histamine mediated. Check the clinical history for foods and drinks ingested
within 60 minutes of symptom onset and for the presence of typical immediate symptoms
such as urticarial rash, angioedema, anaphylaxis and GI upset in context of the other
symptoms. Multiple allergies can develop although this is less common. Any suspected food
triggers would lead to similar symptoms after every exposure and symptoms would not be
expected to occur unless exposure to that trigger had occurred, meaning that if the patient
has eaten a suspected food SINCE the original episode without a problem, that food is
excluded as the allergen.
If the allergen is not easily identified on clinical history further investigation is
recommended via referral to the Peninsula Specialist Immunology and Allergy Service,
Derriford Hospital where skin prick testing and challenge testing can be considered. While
waiting for the appointment the following actions are helpful;
1. Consider performing Specific IgE blood tests but only to foods specifically suspected
from the history; there is no role for screening foods not implicated in the index
reaction. However the presence of Specific IgE does not diagnose allergy and the
results can often be difficult to interpret if the patient is atopic.
2. Prescribe self-injectable adrenaline if there has been any suggestion of airway or
cardiovascular compromise during previous reactions (have a lower threshold for
prescribing in asthmatics). If self-injectable adrenaline is prescribed (2 devices to be
carried at all times), it is important the patient is taught how and when to use them
(see above)
3. Optimise asthma care.
Food Intolerance
Food intolerance is a benign, although unpleasant, condition. Patients typically develop
isolated and sometimes non-specific-gastrointestinal symptoms some hours after eating
varied food groups. Patients will be able to tolerate small amounts of the foods and will find
that the amount tolerated will vary day to day; this is the main differentiating factor from
food allergy. No specific investigations are required and the mainstay of treatment is to
exclude offending food groups. Reintroduction of those food groups periodically is useful as
intolerance can resolve. It is essential that a patient maintain a balanced diet and if multiple
exclusions are necessary the patient may benefit from a dietician review. The Peninsula
Specialist Immunology and Allergy Service has a dedicated allergy-specialist dietician who
accepts appropriate referrals; outside of this context there is little utility in a specialist
allergy review unless Type 1 hypersensitivity to food has not been excluded (see above).
Food allergy and food intolerance do not contribute to eczema in adults. Testing for food
allergy (with specific IgE blood tests) without a supporting clinical history suggestive of type
one hypersensitivity as described above will not be beneficial as the underlying pathology in
eczema is not IgE mediated and results will be influenced by the underlying atopy.