Food Allergies
Immune system reactions to specific foods causing various symptoms.
TL;DR
Immune-mediated reactions to specific food proteins, ranging from hives to anaphylaxis. Diagnosis requires proper testing — self-diagnosis is wrong more often than right — and strict avoidance with an adrenaline plan is the management.
Overview
A food allergy is an immune response to a food protein, most often IgE-mediated and immediate: symptoms appear within minutes to two hours and range from oral itching and hives to vomiting, wheeze and anaphylaxis. Nine foods cause most reactions — milk, egg, peanut, tree nuts, wheat, soy, fish, shellfish and sesame. It is crucial to distinguish allergy from intolerance: lactose intolerance, coeliac disease and histamine intolerance produce real symptoms but through non-allergic mechanisms, they cannot cause anaphylaxis, and they are managed entirely differently. Self-diagnosed food allergy is confirmed by formal testing only about a third of the time, which is why proper diagnosis matters — unnecessary restriction carries its own harms, including nutritional gaps and, in children, loss of tolerance. Diagnosis combines a careful reaction history with skin prick or specific IgE testing, interpreted against that history because positive tests without symptoms mean sensitisation, not allergy. Oral food challenge under supervision is the gold standard when the picture is unclear. Management is strict avoidance, label literacy and, for anyone at risk of anaphylaxis, prescribed adrenaline auto-injectors and a written action plan. Oral immunotherapy now exists for peanut allergy in children, and early introduction of peanut and egg in infancy prevents allergy developing at all.
Common Symptoms
- •Itching or tingling of the lips, mouth and throat within minutes of eating
- •Hives, flushing and facial or lip swelling
- •Vomiting, abdominal pain or diarrhoea after the trigger food
- •Wheeze, cough or throat tightness
- •Anaphylaxis: breathing difficulty, throat closure, dizziness or collapse — an emergency
- •In non-IgE forms: delayed eczema flares, reflux or chronic diarrhoea in infants
Common Causes
- •Peanut, tree nuts, milk, egg, wheat, soy, fish, shellfish and sesame — the major allergens
- •Infant eczema and skin barrier disruption as the main sensitisation route
- •Delayed introduction of allergenic foods in infancy
- •Family history of atopy
- •Cross-reactivity: birch pollen with apple and hazelnut, latex with banana and avocado
- •Non-IgE mechanisms in food protein-induced enterocolitis and allergic proctocolitis
Root Causes
IgE antibodies against specific food proteins arm mast cells and basophils; on re-exposure, the allergen cross-links IgE and triggers degranulation, releasing histamine and mediators that drive symptoms within minutes. Sensitisation develops through a combination of genetic atopic tendency, skin barrier defects in infancy (particularly eczema), and delayed allergen introduction. Non-IgE food allergies involve cell-mediated gut inflammation with delayed, harder-to-diagnose patterns.
How It's Diagnosed
Diagnostic Markers
- A detailed reaction history: food, dose, timing, symptoms and reproducibility — the foundation of diagnosis
- Skin prick testing, sensitive but only meaningful against the clinical history
- Specific IgE blood tests, with component-resolved diagnostics for peanut and nuts
- Supervised oral food challenge — the gold standard when history and tests conflict
- Exclusion of intolerance mimics: lactose breath test, coeliac serology
- Tryptase during severe reactions to confirm anaphylaxis
- Never diagnose by IgG food panels — they measure exposure, not allergy, and are clinically invalid
When to See a Doctor
See an allergist after any suspected food reaction, before re-exposing yourself or your child. Seek emergency care immediately for breathing difficulty, throat tightness, tongue swelling, widespread hives with vomiting, dizziness or collapse after eating — and use an adrenaline auto-injector if one is prescribed, then call emergency services even if symptoms improve. Get reviewed if you are restricting multiple foods without a confirmed diagnosis.
Supplements Studied For This
Diet & Lifestyle
Suggested Pattern
The dietary management is precise avoidance, not broad restriction. Diagnosis must be confirmed before eliminating foods, because unnecessary elimination is nutritionally risky and can convert tolerance into allergy in children. Label literacy is a core skill, including precautionary may-contain statements and the non-food sources of allergens. For infants, the LEAP trial evidence changed practice: introducing peanut early, around 4-6 months in high-risk infants under guidance, reduces peanut allergy development by over 80%. Baked egg and milk ladders safely reintroduce these foods in baked form for many allergic children under specialist care.
Eat more
- Everything except your confirmed allergens — restriction beyond that is harmful
- Early, guided introduction of peanut and egg in infancy to prevent allergy developing
- Nutritionally equivalent substitutes: calcium-rich alternatives for milk allergy, varied proteins for multiple allergies
- Baked forms of milk or egg where your allergist confirms a ladder approach is appropriate
Avoid
- Your confirmed allergens only, in all forms and preparations
- Foods with precautionary allergen labelling if your allergist advises strict avoidance
- High-risk settings for cross-contact: buffets, bakeries and shared fryers
- Never re-challenge a suspected allergen at home after a significant reaction
Supporting Research
Randomized trial of peanut consumption in infants at risk for peanut allergy
AR101 oral immunotherapy for peanut allergy
Randomized trial of introduction of allergenic foods in breast-fed infants
Administration of a probiotic with peanut oral immunotherapy: a randomized trial
Vitamin D insufficiency is associated with challenge-proven food allergy in infants
Frequently Asked Questions
Who It Affects
True food allergy affects roughly 1-2% of adults and 4-8% of children, while self-reported food allergy runs three to four times higher.
Most food allergy begins in childhood, and milk, egg, wheat and soy allergies are commonly outgrown by school age, whereas peanut, tree nut, fish and shellfish allergies usually persist. Adult-onset allergy does occur, most often to shellfish. Children with moderate-to-severe eczema carry the highest risk of developing food allergy in infancy.
Lifestyle Tips
- •Get formally diagnosed before eliminating foods — most self-diagnosed allergies are wrong
- •Carry two adrenaline auto-injectors at all times if prescribed, and check expiry dates
- •Train family, school and colleagues to recognise anaphylaxis and use your injector
- •Read every label every time — formulations change without notice
- •Wear medical alert identification for severe allergies
- •Use adrenaline early in anaphylaxis; antihistamines do not treat airway or circulation symptoms
- •Ask about oral immunotherapy for children with persistent peanut allergy
- •Introduce allergens early in your infant under paediatric guidance — delay creates allergy rather than preventing it
My Notes
Sign in to add personal notes
This information is for educational purposes only. Always consult a healthcare professional before starting any supplement regimen.