Allergy is a extremely broad topic encompassing many different diagnoses and clinical presentations. Whilst there is still a lack of convincing evidence to guide practice in many areas, there is also a considerable degree of misinterpreted information pertaining to diagnosis, investigation and management
Allergic disease is increasing in most areas of the world, including Australia. Severe allergic reactions (anaphylaxis) can result in death, whilst many conditions like eczema and hayfever impact significantly on quality of life.
Whilst there is evidence of rapidly increasing rates of anaphylaxis, food and environmental allergies, there is also considerable over-diagnosis. In the paediatric population, inappropriately restricted diets and other treatments can potentially be harmful, which underpins the value of accurate diagnosis and monitoring, wherever possible.
Definitions and terminology
Urticaria (hives) is an allergic reaction isolated to the skin, characterized by redness, itch, wheals and flares. Urticaria is a common symptom of an acute allergic reaction to food, medications or insect bites/stings. It does not constitute anaphylaxis, although can be associated with it. Urticaria can also occur as a reaction to viral or bacterial infections or physical triggers like cold, vibration, pressure etc. A cause for urticaria is often not found (idiopathic). Urticaria can also become chronic, in which a case further assessment is indicated. See RCH Clinical Practice Guidelines for more information, including management and indications for referral.
Angioedema is a swelling of the subcutaneous and soft tissues of the body. Angioedema is not anaphylaxis, although can be associated with it. A cause for angioedema is often not found, although it can be associated with rare conditions such as C1-esterase inhibitor deficiency. See RCH Clinical Practice Guidelines for more information, including management and indications for referral.
Anaphylaxis is a potentially life-threatening IgE-mediated allergic reaction. For further information please see the anaphylaxis pre-referral guideline, and the RCH Clinical Practice Guidelines. The ASCIA anaphylaxis management plans are recommended.
Allergic reactions constitute a reaction of the immune system to a wide variety of proteins in foods, medications, insect bites and environmental allergens like pollens, saliva, animal dander etc. The diagnoses is mainly clinical, with investigations only adding to the clinical picture in select scenarios. It is important to distinguish acute IgE-mediated reactions from delayed non-IgE mediated reactions.
Acute IgE mediated reactions (including anaphylaxis)
Includes urticaria and angioedema, oral allergy syndrome, some food allergies and anaphylaxis
The onset of symptoms is within 2 hours (mostly within 15- 60 minutes) of exposure/ingestion and usually resolves within 12 hours. These include:
- Cutaneous reactions such as acute urticaria, pruritis and angioedema
- Respiratory symptoms such as acute rhinoconjunctivitis, cough, wheeze and stridor
- Cardiovascular symptoms, including pallor, collapse as a result of hypotension syndrome
- Symptoms of milder allergic reactions include swelling of the lips/face/eyes, hives or welts, tingling mouth, abdominal pain or vomiting.
- The most severe and potentially life-threatening IgE-mediated reaction is anaphylaxis, which is clinically diagnosed (see anaphylaxis pre-referral guideline).
Serum-specific IgE (RAST) and skin prick testing (SPT) are useful tests in this group of reactions.
True IgE-mediated food allergies are acute and reproducible. Common allergens include cow’s milk protein, peanut, tree nuts, egg, wheat, sesame and seafood. Cow’s milk and egg allergies are commonly outgrown during childhood, whereas the chance of outgrowing peanut and tree nut allergies is only around 20%.
Non-IgE mediated reactions
Includes food-protein induced enteropathy (including proctocolitis) and food protein induced enterocolitis syndrome (FPIES - see ASCIA website FPIES) and many food allergies.
Symptoms occur hours to days after ingestion/exposure and may continue for many days. Symptoms are less specific and include diarrhoea, vomiting, colic/pain, gastro-oesophageal reflux, food refusal/aversion and blood in stool.
Unfortunately no clinical test exists to quantify or monitor these reactions. Diagnosis is based on clinical history, elimination diet (2–6 weeks), followed by a trial of re-introduction.
Common triggers for this group, often referred to as intolerances rather than allergies, include cow's milk protein and soy protein. Both are generally self resolving within the first years of life.
Note that abdominal symptoms are commonly seen when food is too spicy/rich, which is not an allergy. Peri-oral dermatitis with ‘acidic’ foods like strawberries and tomatoes is also a common non-allergic food reaction.
- Allergies are increasingly common, although despite this, considerable over-diagnosis does exist.
- Allergies are largely clinical diagnoses, with investigations only useful in select scenarios.
- Skin prick testing (SPT) and RAST will only identify immediate onset (IgE-mediated) allergies.
- Positive SPT and/or RAST without a history of clinical reaction on prior exposure only constitutes sensitisation, rather than allergy. Foods should not be routinely excluded from the diet based on positive SPT or RAST results without a positive clinical reaction.
- SPT or RAST should not be used to predict whether a child will be allergic to a food that has never been offered.
- Infant food introduction advice is to start solids from 4 months onwards and to rapidly expand the variety in the diet and progressively include more allergenic foods like egg and nuts (see ASCIA infant weaning guideline).
- Testing for preservatives, additives and cosmetics is not generally useful or recommended.
- Anaphylaxis: this is an emergency and should be managed in an Emergency Department - please see the RCH Clinical Practice Guidelines for further details.
- Food allergy: if a severe reaction has occurred, we suggest avoidance of the offending agent until
assessed by specialist services. Cow's milk and soy protein allergy management includes maternal dairy/soy exclusion whilst breast feeding or use of extensively hydrolysed or elemental infant formulas (paediatrician only authority script).
- Urticaria and angioedema: these are generally managed symptomatically (see RCH urticaria and angioedema CPGs for further information).
- Skin prick testing and allergy consultations are available though Paediatrics Ballarat or the Ballarat Allergy Clinic as private services. The focus is on food allergy, eczema and environmental allergens that trigger asthma and eczema.
- Currently the services offered in Ballarat do not include testing for drug allergies (although challenges may be offered in select circumstances) or insect allergies.
- Following assessement by a paediatrician with an interest in allergy, a secondary referral to dietetic services may be indicated.
- Other resources