Allergy Testing in Children: When It's Useful, When It's Not

A child with a rash, a mysterious reaction, or a chronic symptom often gets sent for 'allergy testing' — a broad term that hides very different tests with very different reliability. Understanding what test does what, and when testing is actually useful, prevents unnecessary panels that produce false positives and food restrictions that weren't needed.

The main types of allergy tests

• Test: Skin prick test · How it works: Small allergen on skin; wheal if positive · Best for: IgE-mediated allergies · Limitations: Not for eczema, drug allergies well
• Test: Specific IgE blood test (RAST) · How it works: Blood test for antibodies to allergens · Best for: When skin test not possible · Limitations: False positives; needs clinical correlation
• Test: Patch test · How it works: Allergens on skin patch 48 hours · Best for: Contact dermatitis · Limitations: Specific to skin-touch allergens
• Test: Food challenge (supervised) · How it works: Eat suspected food under observation · Best for: Definitive food allergy diagnosis · Limitations: Requires clinical setting, some risk
• Test: Elimination diet + reintroduction · How it works: Remove suspected food, watch, add back · Best for: Suspected food intolerance · Limitations: Time-intensive, needs specialist guidance
• Test: Component-resolved testing · How it works: IgE to specific proteins within allergens · Best for: Distinguishing true allergy from cross-reactivity · Limitations: Specialist interpretation needed

The specific problem with broad panels

• Panels test dozens of allergens without clinical suspicion.
• False positive rate is high — 10-40% of children test positive to a food they eat regularly without symptoms.
• Result: unnecessary food restriction based on lab positive without actual reaction.
• Cost: expensive panels for little clinical value.
• A positive test without a matching reaction is not an allergy — it's sensitisation.

When testing is genuinely useful

• Suspected specific allergen after a clear reaction — target the specific test.
• Anaphylaxis with unclear trigger — comprehensive workup.
• Eczema with suspected food trigger — carefully evaluated.
• Persistent asthma with environmental trigger workup.
• Recurring hives without clear cause.
• Before certain drugs (penicillin skin test in specific cases).

When testing is NOT useful

• Vague symptoms with no specific reaction pattern.
• General screening 'to see what he's allergic to'.
• Chronic non-specific complaints.
• For food intolerances (not IgE-mediated — testing doesn't detect these).
• Alternative medicine 'allergy panels' (bioresonance, hair testing, etc.) — no evidence base.

The specific common allergies in Indian children

• Cow's milk (usually outgrown by 3-5).
• Egg (usually outgrown by 5).
• Wheat (usually outgrown; celiac is different).
• Peanut, tree nuts (often persistent).
• Shellfish (often persistent).
• Sesame (increasing recognition).
• Fruits and vegetables (often oral allergy syndrome).
• Environmental: dust mite, pollens, animal dander, mould.

The specific record for a confirmed allergy

• Allergen (specific — 'peanut' not 'nuts').
• How diagnosed (clinical, skin test, blood test, challenge).
• Date diagnosed.
• Reaction history — every event with date, exposure, symptoms, treatment.
• Severity — mild, moderate, severe/anaphylaxis.
• Current management — avoidance, medications, EpiPen if prescribed.
• Reassessment plan — many food allergies outgrown; retest at intervals.

The specific role of the specialist

• Paediatric allergist for complex or severe cases.
• General paediatrician for straightforward evaluations.
• Dermatologist for skin manifestations.
• Pulmonologist for respiratory.
• Avoid multiple opinions without coordination — different specialists may recommend different testing.

For confirmed food allergy — the school piece

• Written allergy action plan.
• EpiPen at school (in nurse's office or child's bag).
• Teacher, canteen staff aware.
• Safe food policy for classroom.
• Regular updates as tolerance changes.

Testing is a tool for confirming clinical suspicion, not a screening panel. Used well, it protects the child; used broadly, it creates restrictions without benefit.

References

• AAAAI — allergy testing guidelines
• IAP — pediatric allergy India
• PMC — allergy testing overuse