Allergies and Sensitivities

Food allergies

~1 in 10 children have a food allergy — usually paired with a history of asthma, eczema or rhinoconjunctivitis. Most common triggers: egg, cow’s milk, peanut, tree nut, seafood, sesame, soy, fish, wheat. Most are not severe and may be outgrown with time — but peanut, tree nut, seed and seafood allergies tend to be lifelong. Some reactions can be severe, rarely causing anaphylaxis.

Environmental allergies

Triggered by inhaled or dermal exposure rather than ingestion — similar outcomes to food allergy, but rash/dermatitis and/or respiratory symptoms are more prominent.

Anaphylaxis and angioedema

(See dermatology for the skin-focused management.) Emergency treatment is ALS-based: prompt adrenaline 1:1000, 0.1 mL/kg IM, repeated every 5 minutes until response, alongside airway/shock management as per ALS. IV hydrocortisone does not treat acute anaphylaxis — it reduces the response and likelihood of relapse within the same event (e.g. from ongoing food digestion).

Assessing non-life-threatening allergy

History is the mainstay of diagnosis. Take a detailed history: timing of symptom onset; nature/extent (which organ systems); duration; reproducibility on prior exposure; other factors needed to trigger symptoms (e.g. exercise).

Refer to a specialist if

• Suspected IgE-mediated food allergy — rapid onset (within 30–60 min), can involve multiple systems: skin (urticaria/angioedema), GI (vomiting, diarrhoea, abdominal pain), respiratory (cough, wheeze, stridor, chest tightness, voice change, tongue swelling), cardiovascular (hypotensive shock/collapse).
• Suspected non-IgE-mediated food allergy — delayed onset (hours to days), predominantly GI symptoms. 10–15% present as food protein-induced enterocolitis syndrome (FPIES) — severe vomiting, hypotensive shock and collapse. No specific test — diagnosis is by elimination and (when appropriate) rechallenge.
• Asthma requiring preventer therapy.
• Allergic rhinoconjunctivitis not responding to maximal medical therapy — an indication for immunotherapy.
• Atopic dermatitis with poor response to topical management.
• Suspected drug or latex allergy.
• Systemic reaction to an insect sting — an indication for immunotherapy if available.

Do NOT refer for

A single episode of idiopathic urticaria (no identified cause); autism/ behavioural disease (history is hard to ascertain); migraine as the only symptom of irritant exposure; reactions to respiratory irritants (smoke, perfume).

Specialist testing

• Skin prick testing (SPT) — good for allergen-specific IgE (foods, aeroallergens, some venoms, antibiotics, latex). Quick, cheap, rapid results, but must be done by a trained specialist with resuscitation skills available. Requires 4–6 weeks after an acute anaphylactic reaction; not performed with widespread skin disease/dermatographism. Antihistamines (withhold 4 days), H2 antagonists (1 day), or TCAs/ neuroleptics (2 weeks) need to be stopped beforehand — unless the risk of doing so (e.g. seizures) is too high, in which case skip SPT. Positive predictive value alone is <50%, but combined with a clear history it’s confirmatory; may need reinforcement with a formal oral food challenge if history is uncertain.
• RAST — detects free antigen-specific IgE in serum; less sensitive/ specific than SPT and not always available; Medicare limits to 4 allergens per test. Useful when SPT is contraindicated, unaffected by prior medication, and safe soon after recent anaphylaxis (it’s just a blood test). Latex and drug allergy can also be tested this way.
• Oral food challenge — the gold standard. Specialist-only, in a safe clinical setting (half-day hospital admission); incremental food doses with monitoring; placebo, single- or double-blind protocols; disguising vehicles may be used (patients can have a psychological response to a known allergen).

Management

Avoidance is the mainstay once a relevant allergen is confirmed — a dietitian should be involved if multiple foods are avoided. If aeroallergens exacerbate asthma/atopic dermatitis/allergic rhinitis and avoidance or maximal medical therapy aren’t sufficient, consider desensitisation (immunotherapy).

Develop an allergy management plan with the family; if anaphylaxis is a feature, discuss reaction recognition and EpiPen Jr use/storage — desensitisation therapy is recommended for these patients.

Regular specialist follow-up matters, especially for food allergy — most children develop tolerance to wheat, milk, egg and soy by age 5–6, so periodic reassessment (± repeat SPT every 1–2 years) identifies when foods no longer need avoidance, easing the family’s burden. For lifelong allergens, periodically re-review the management plan as the child grows.

Unorthodox testing — avoid

Vega testing, kinesiology, radionics, pulse testing, iridology, hair analysis and voice bio-testing are inappropriately marketed for allergy diagnosis without a supporting reaction history. These typically measure IgG4 antibodies, which are found in healthy children and simply reflect allergen exposure, not an allergic response — an inappropriate basis for diagnosing allergy.