Latex allergy — branching viva

Stem

The examiner moves from classification of latex sensitivity, to the Hev b component framework, to intraoperative anaphylaxis, and finishes on latex-fruit syndrome and primary prevention. [1] [4]

Branch 1 — Classification: three mechanisms, one trigger material

Examiner: A child gets a rash from rubber gloves. What are the three immune mechanisms of latex sensitivity, and why does the distinction matter? [1]

Strong answer: The three forms are Type I IgE-mediated allergy, Type IV allergic contact dermatitis, and irritant contact dermatitis. Type I is IgE to latex proteins (Hev b) — immediate, mast-cell-driven, causes urticaria to anaphylaxis. Type IV is T-cell-mediated delayed hypersensitivity to rubber accelerators (thiurams, carbamates) — eczematous, 24 to 72 hours, confirmed by patch testing. Irritant dermatitis is non-immune barrier disruption from wet work and friction. The distinction matters because the management is completely different: latex-free environment plus adrenaline for Type I, accelerator-free gloves and emollients for Type IV, and barrier repair for irritant. Only Type I is dangerous. [1] [4]

Branch 2 — The Hev b component framework

Examiner: Walk me through the Hev b components. Which matter for spina bifida, which for latex-fruit syndrome, and which can be ignored? [8]

Strong answer: The major IgE-reactive latex allergens are the Hev b proteins. Hev b 1 (rubber elongation factor) and Hev b 3 are dominant in spina bifida patients, reflecting direct mucosal contact with raw latex particles from catheters and gloves — high clinical relevance. Hev b 5 is a major allergen in healthcare workers and children, also high clinical relevance. Hev b 6.01 (hevein) drives latex-fruit syndrome through cross-reactivity with plant class I chitinases in banana, kiwi, avocado and chestnut. Hev b 8 (profilin) is a low-relevance marker — it cross-reacts with pollen profilins and often represents sensitisation without genuine latex clinical reactivity. Quercia and colleagues showed that patients monosensitised to Hev b 8 may safely undergo surgery in a normal environment. [8] [10]

Branch 3 — Intraoperative anaphylaxis

Examiner: A five-year-old with spina bifida collapses 40 minutes into elective surgery. No new drug since induction. What is happening, and what do you do? [12]

Strong answer: This is intraoperative latex anaphylaxis — a clinical diagnosis. The delayed onset (30 to 60 minutes into surgery) distinguishes it from drug-triggered anaphylaxis, which fires immediately at induction. Give IM adrenaline into the anterolateral thigh first (roughly 0.01 mg/kg of 1:1000, or a weight-banded autoinjector); call for help; lie flat, oxygen and IV fluids for shock; bronchodilator adjunctive; repeat adrenaline at five minutes if no response; remove all latex from the environment and eliminate powdered latex gloves from the entire suite. After the event, follow the perioperative anaphylaxis pathway: serial tryptase, specialist allergy referral, and document the latex-safe requirement. Long term: strict latex avoidance, latex-safe surgery for all future procedures, adrenaline autoinjector, action plan, and medical alert. [12] [5]

Branch 4 — Latex-fruit syndrome

Examiner: A latex-allergic child reacts to banana. Explain the mechanism and the counselling. [6]

Strong answer: This is latex-fruit syndrome. Hev b 6.01 (hevein) in latex shares epitopes with class I chitinases in certain fruits — banana, kiwi, avocado, chestnut, passion fruit, tomato and others. IgE primed by latex cross-reacts with these plant defence proteins, so the child reacts to foods the family may never have linked to latex. Up to half of latex-allergic patients react to at least one fruit. Counsel the family to be cautious with these foods and to avoid only those that cause reactions, because not all latex-allergic children react to every cross-reactive food. The reaction can range from oral itching to anaphylaxis, so assess severity individually. [6]

Branch 5 — Primary prevention

Examiner: Why has latex allergy declined since the 1990s, and what is the evidence? [11]

Strong answer: The decline is driven by the switch to powder-free, low-protein gloves. Powdered latex gloves aerosolise latex protein on cornstarch, driving both contact and airborne sensitisation. Removing powder eliminates the airborne route, and reducing protein content lowers the antigen load. The German primary prevention study (Allmers 2002) demonstrated this in healthcare workers — switching to powder-free, low-protein gloves dramatically reduced sensitisation. It is a landmark evidence-based public health intervention. However, latex allergy persists in high-risk groups: spina bifida, multi-surgery children, and previously-sensitised individuals. So while the general population benefits, the high-risk child still needs latex-safe protocols and active screening. [11] [5]

Examiner extras

• Any child with spina bifida gets latex-safe surgery until tests prove otherwise — never gamble on the first procedure. [5]
• Sensitisation is not allergy: a positive IgE without a reaction history does not justify latex avoidance or latex-safe surgery. [1]
• Powdered latex gloves elsewhere in the operating suite can trigger a reaction even if the patient's own gloves are latex-free — eliminate them from the suite. [4]
• Latex-fruit syndrome affects up to 50 per cent of latex-allergic patients — ask about banana, kiwi, avocado and chestnut in every latex-allergic child. [6]