| Feature | Food Allergy | Food Intolerance |
|---|---|---|
| Immune system involvement | Yes — immune-mediated response | No — non-immune mechanism |
| Mechanism | IgE antibodies (or T-cell mediated) | Enzyme deficiency, pharmacological, or sensitivity |
| Onset | Rapid (minutes to 2 hours for IgE-mediated) | Delayed (hours to days) |
| Dose | Small amounts can trigger severe reaction | Usually dose-dependent — small amounts may be tolerated |
| Severity | Can be life-threatening (anaphylaxis) | Uncomfortable but rarely life-threatening |
| Symptoms | Skin, respiratory, GI, cardiovascular | Primarily GI, sometimes headaches, fatigue |
KEY TAKEAWAY: Allergy = immune response (IgE-mediated); Intolerance = non-immune reaction. This distinction drives both risk assessment and management strategies.
Sensitisation phase (first exposure):
1. Allergen is absorbed into body
2. Immune system incorrectly identifies it as a threat
3. B cells produce IgE antibodies specific to that allergen
4. IgE antibodies bind to mast cells (in tissues) and basophils (in blood)
Reaction phase (subsequent exposures):
1. Allergen enters body again
2. Binds to IgE antibodies on mast cells/basophils
3. Triggers mast cell degranulation — release of histamine, prostaglandins, leukotrienes
4. Causes the classic allergy symptoms
Symptoms (SAMPLERS mnemonic):
- Skin: Urticaria (hives), angioedema (swelling), eczema
- Respiratory: Wheeze, cough, runny nose, throat tightening
- GI: Nausea, vomiting, abdominal pain
- Cardiovascular: Drop in blood pressure, rapid/weak pulse
Anaphylaxis: Severe, life-threatening systemic allergic reaction
- Involves multiple body systems simultaneously
- Can cause airway constriction, circulatory collapse, death
- Treated with adrenaline (epinephrine) — EpiPen
Food Standards Australia New Zealand (FSANZ) requires mandatory declaration of 14 allergens on food labels:
EXAM TIP: VCAA may ask you to identify major allergens. Know the FSANZ list. Peanuts, tree nuts, milk, eggs, wheat, soy, fish, shellfish, and sesame are the most commonly tested.
Management of food allergies:
- Strict allergen avoidance — read all food labels
- Carry adrenaline auto-injector (EpiPen) for anaphylaxis risk
- Action plan — know what to do in an emergency
- Advise food preparers (restaurants, schools) about allergy
- Cross-contact risk — separate utensils, surfaces, oils
Cause: Deficiency of lactase enzyme in the small intestine
- Without lactase, lactose (milk sugar) cannot be hydrolysed into glucose + galactose
- Undigested lactose passes to large intestine where bacteria ferment it
Symptoms (GI-focused, dose-dependent):
- Bloating, flatulence
- Abdominal cramping
- Diarrhoea
- Nausea
Management:
- Reduce or eliminate lactose-containing dairy
- Use lactase enzyme supplements before consuming dairy
- Choose lactose-free dairy products
- Small amounts of aged cheese and yoghurt are often tolerated (lower lactose content)
- Ensure adequate calcium from lactose-free dairy alternatives (fortified plant milks)
Gluten is a protein found in wheat, rye, barley, and triticale.
COMMON MISTAKE: Coeliac disease is NOT an allergy — it is an autoimmune condition. Do not call it a gluten allergy in exam responses. Use the term “autoimmune” or “immune-mediated intolerance.”
FODMAPs = Fermentable Oligo-, Di-, Monosaccharides And Polyols
FODMAPs are short-chain carbohydrates poorly absorbed in the small intestine:
| FODMAP Category | Examples | Food Sources |
|---|---|---|
| Oligosaccharides (fructans, GOS) | Fructans, galactooligosaccharides | Wheat, rye, onion, garlic, legumes |
| Disaccharides (lactose) | Lactose | Milk, soft cheeses, ice cream |
| Monosaccharides (excess fructose) | Fructose > glucose | Apples, honey, high-fructose corn syrup |
| Polyols (sugar alcohols) | Sorbitol, mannitol | Stone fruits, mushrooms, sugar-free gum |
Mechanism:
1. FODMAPs reach the large intestine undigested
2. Gut bacteria rapidly ferment them → gas production → bloating, distension
3. FODMAPs are osmotically active → draw water into bowel → diarrhoea
Who is affected: People with Irritable Bowel Syndrome (IBS) are most sensitive
Management:
- Low-FODMAP diet (developed by Monash University, Melbourne)
- Elimination phase: remove all high-FODMAP foods for 2–6 weeks
- Reintroduction phase: systematically test individual FODMAPs to identify triggers
- Maintenance: personalised diet avoiding individual triggers
VCAA FOCUS: Know FODMAP as an acronym (fermentable oligosaccharides, disaccharides, monosaccharides and polyols), understand the fermentation mechanism causing symptoms, and distinguish it from allergy. Monash University developed the Low-FODMAP diet — this is an Australian connection examiners may test.
