Chapter 28 — Key Takeaways

One page.

⚠️ Six Mechanisms, One Word

⚠️ Coeliac disease and IgE allergy are where small amounts count. Almost everything else is a THRESHOLD — so the question is usually "how much," not "never."

⚠️ Self-reported food allergy runs several times higher than challenge-confirmed allergy — roughly a fifth of adults report one, confirmed prevalence is low single digits. That gap costs the person with the real one.

⚠️ "It's nocebo" is not "you're making it up." In blinded challenges a substantial proportion react to placebo, through real physiological pathways. The symptoms are real; the trigger isn't the food.

⚠️ §28.3 — ANAPHYLAXIS

⚠️ INTRAMUSCULAR ADRENALINE, ANTEROLATERAL THIGH, FIRST LINE. NO ABSOLUTE CONTRAINDICATION. DELAY IS ASSOCIATED WITH DEATH.

⚠️ ANTIHISTAMINES DO NOT TREAT ANAPHYLAXIS. Reaching for one instead of adrenaline is the most common fatal error.

Recognition: skin (hives, swelling) · ⚠️ airway (throat tightness, hoarse voice, stridor) · ⚠️ breathing (wheeze, persistent cough, breathlessness) · ⚠️ circulation (faintness, collapse, pallor, floppiness in an infant, confusion) · gut · ⚠️ a sense of impending doom.

⚠️ THE RULE THAT REMOVES HESITATION: airway, breathing or circulation involvement — or two or more systems — after a likely exposure. Give adrenaline.

⚠️ Skin signs are NOT required. A substantial minority of fatal cases had no rash. Waiting for hives is waiting for something that may not come.

Then: call emergency services · ⚠️ lie flat with legs raised (sitting if breathless, side if vomiting) — ⚠️ never stand them up · second dose after ~5 min if no improvement · observe, because biphasic reactions occur.

⚠️ Fatal-outcome risk factors: asthma, especially poorly controlled (the big one) · ⚠️ adolescence and young adulthood · peanut and tree nut · delayed adrenaline · being upright.

⚠️ Cofactors — exercise, alcohol, NSAIDs, infection, menstruation — can convert a tolerated exposure into anaphylaxis. ⚠️ And infants present with sudden floppiness, pallor, persistent crying, drooling or vomiting, because they cannot report throat tightness.

⚠️ Two devices, carried everywhere, in date. A device at home is a device you don't have.

⚠️ §28.4 — Sensitization Is Not Allergy

Skin prick and specific IgE measure SENSITIZATION. ⚠️ Oral food challenge measures ALLERGY.

⚠️ THE HISTORY DRIVES THE TESTING. THE TESTING DOES NOT DRIVE THE DIAGNOSIS.

⚠️ Broad-panel testing without a suggestive history generates false positives, each of which generates an unnecessary elimination — and removing foods like peanut and egg can INCREASE the chance of developing true allergy (§28.14). Component testing improves specificity.

§28.5–28.6 — Coeliac Disease

⚠️ AUTOIMMUNE. Not an allergy, not an intolerance. ~1% prevalence, largely undiagnosed, HLA-DQ2/DQ8.

⚠️ Frequently NOT gastrointestinal: iron-deficiency anaemia · fatigue · osteoporosis · raised liver enzymes · mouth ulcers · dermatitis herpetiformis · infertility and recurrent miscarriage · neurological symptoms · short stature. ⚠️ Anyone with unexplained iron-deficiency anaemia should be screened.

Serology: tTG-IgA WITH total IgA (IgA deficiency is commoner in coeliac and causes false negatives). Treatment: strict, lifelong. ⚠️ Small amounts cause damage, frequently without symptoms — so "a little bit doesn't affect me" is not evidence it's safe.

⚠️ §28.6 — THE MOST ACTIONABLE INSTRUCTION IN THE CHAPTER: TEST BEFORE REMOVING GLUTEN.

Serology and biopsy both normalize on a gluten-free diet. The only way back is a deliberate weeks-long GLUTEN CHALLENGE, which many refuse — ⚠️ leaving a lifelong restriction with no diagnosis, no follow-up, no bone monitoring, and no answer for relatives who should be screened.

⚠️ The diet in practice: cross-contact (toasters, boards, flour dust) · hidden sources (soy sauce, malt vinegar, some medications) · oats usually fine but heavily cross-contaminated · ⚠️ replacement products are lower in fibre, iron and B vitamins and several times the price · ⚠️ the commonest error is swapping every wheat product for a packaged gluten-free one — better: rice, potatoes, buckwheat, quinoa, certified oats, beans.

§28.7 — Lactose Intolerance Is the Global Norm

⚠️ Lactase PERSISTENCE is the derived, unusual trait. Roughly two-thirds of the world's adults are non-persistent, varying enormously by ancestry. ⚠️ Normal physiology, not a disease.

Strongly dose-dependent — most tolerate ~12 g (a cup of milk), especially with food and spread out · hard cheese is very low in lactose · yoghurt contains bacterial lactase · lactase supplements work · ⚠️ post-gastroenteritis intolerance is TEMPORARY.

⚠️ Don't eliminate dairy entirely — calcium, and Chapter 25's sixty-year bone story.

🟡 §28.8 — Non-Coeliac Gluten Sensitivity

⚠️ Blinded rechallenge has repeatedly failed to reproduce symptoms with gluten once FODMAPs were controlled, with substantial nocebo rates. A 2018 Gastroenterology crossover (Skodje et al.) found FRUCTAN provoked symptoms and gluten did not.

Candidates: ⚠️ FODMAPs · amylase-trypsin inhibitors · nocebo.

⚠️ Both halves: something real is happening in at least some people, and gluten is probably not the agent in most. "There's nothing wrong with you" is unkind and unsupported. "You have a gluten problem" is also unsupported, and commits them to a lifelong restriction aimed at the wrong molecule.

⚠️ The pathway: exclude coeliac FIRST while eating gluten → exclude wheat allergy → structured FODMAP process with reintroduction → ⚠️ which usually means eating SOME wheat rather than none.

§28.9 — The Others

Oral allergy syndrome: pollen cross-reactivity, itchy mouth, ⚠️ heat-labile proteins so cooked forms are generally tolerated — reassuring, and worth assessing rather than dismissing. Histamine intolerance: 🟡 contested, tests unreliable. Sulphites: 🟢 real, especially in asthma. Colours + benzoate and hyperactivity: 🟡 real, modest, contested. Tyramine + MAOIs: a genuine drug–food interaction. ❌ MSG.

⚠️ §28.9b — the language point: the MSG syndrome was named after a CUISINE, not a compound or a symptom, while glutamate in parmesan, tomatoes, mushrooms and breast milk acquired no syndrome. It survived decades of failed blinding because the framing did work the evidence never had to.

⚠️ Language allocates seriousness. When "allergy" does six jobs it stops functioning as a warning — and the person it protects loses the protection.

Use "allergy" for allergy, "coeliac disease" for coeliac disease, and "I don't tolerate it well" for everything else. It costs nothing.

❌ §28.10 — The Tests That Don't Work

⚠️ IgG food panels measure EXPOSURE — and possibly tolerance. The test reliably identifies what you eat. Major allergy and immunology bodies have issued explicit statements against their use. Also invalid: hair analysis · applied kinesiology · VEGA/electrodermal · cytotoxic and leucocyte assays · iridology · pulse testing.

⚠️ The harm is not the fee: unnecessary elimination · nutritional inadequacy · social and psychological restriction · and DELAYED DIAGNOSIS of coeliac disease, IBD or genuine allergy.

⚠️ §28.11 — The Restriction Pattern, Fourth Instance

Cancer (Ch 26) · CKD (Ch 26) · IBS (Ch 27) · and here — the purest form, because ⚠️ THE RESTRICTION IS GENERATED BY A TEST, which supplies apparent objectivity, specificity, and an explanation for years of symptoms.

⚠️ And the elimination usually helps at first, because removing twenty-three foods removes a bundle. The test appears validated by the outcome. It isn't — the bundle is.

§28.13 — Immunotherapy

⚠️ DESENSITIZATION IS NOT TOLERANCE. The threshold rises while treatment continues; it is not a cure; protection is lost if dosing stops. ⚠️ You still avoid, still carry adrenaline, still read labels.

Costs: common adverse reactions · ⚠️ some analyses find MORE anaphylaxis during treatment than with avoidance · eosinophilic oesophagitis in a minority · years of daily adherence. Also emerging: epicutaneous immunotherapy; ⚠️ anti-IgE (omalizumab, US approval 2024).

⚠️ The trade is DISTRIBUTED versus CONCENTRATED risk — more managed reactions now, less severe unsupervised risk later. A values decision; the family is the right decision-maker.

✅ §28.14 — Prevention

Introduce peanut and egg from around six months in age-appropriate forms and ⚠️ KEEP THEM IN THE DIET REGULARLY. ⚠️ Severe eczema or existing allergy → assess first. Dual-allergen exposure hypothesis: sensitization through inflamed skin, tolerance through the gut.

⚠️ §28.14b's uncomfortable row: decades of guidance advised DELAYING allergenic foods, was followed conscientiously, and probably caused harm while it stood. Stale guidance isn't only a failure to update — sometimes the advice was actively harmful. ⚠️ An argument for humility about current recommendations, including this chapter's.

🧾 Economics

⚠️ The two unavoidable costs — adrenaline auto-injectors where not funded, and the gluten-free premium — fall on the people with the REAL diagnoses, and neither is a nutrition problem. ⚠️ And the expensive tests generate the expensive diets: a £249 panel removing 23 foods commits someone to specialty products indefinitely. Against: coeliac serology is a blood test · FODMAP reintroduction GIVES FOOD BACK · early allergen introduction is peanut butter and egg.

What To Do

1. ⚠️ Two devices, in date, carried. Adrenaline early. Never antihistamines instead. 2. ⚠️ Test before removing gluten. 3. Unexplained iron deficiency → coeliac serology. 4. Dairy: find the threshold. 5. ⚠️ Don't buy an IgG panel. 6. ⚠️ Get a diagnosis before you get a diet. 7. Introduce allergens early and keep them in. 8. ⚠️ A growing avoid-list is the finding. 9. ⚠️ Use the word "allergy" for allergy.

⚠️ Six of nine are about NOT eliminating, or eliminating less. The dominant error is over-restriction — and the single exception, the person with genuine IgE allergy or coeliac disease, needs the opposite advice delivered with total seriousness. Getting those two groups the right advice, and not each other's, is the entire clinical problem.

One Thing to Remember

⚠️ Five of the six people at that table did not have an allergy — and the sixth is the one who pays for it.