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Allergy in a ‘nutshell’ GP guide to survival

Allergy in a ‘nutshell’ GP guide to survival. Dr Gillian Vance. Allergy care. Starts with early diagnosis. Session. Better understanding of the basic immunological mechanisms underlying food allergic disease Apply mechanisms to clinical evaluation & appropriate therapy . Objectives.

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Allergy in a ‘nutshell’ GP guide to survival

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  1. Allergy in a ‘nutshell’GP guide to survival Dr Gillian Vance

  2. Allergy care Starts with early diagnosis

  3. Session • Better understanding of the basic immunological mechanisms underlying food allergic disease • Apply mechanisms to clinical evaluation & appropriate therapy

  4. Objectives • Recognise typical features of allergic disease • Appreciate areas of complexity • Explain what, how & why we evaluate at the allergy clinic

  5. ‘Allergy’ • 1st coined in 1906 by Austrian paediatrician, Clemens von Pirquet • ‘altered reactivity’ to any antigenic stimulation, whether • Immunity – protection • Hypersensitivity – adverse clinical response

  6. ‘Allergy’ • ‘An exaggerated sensitivity to a substance (allergen) that is inhaled, swallowed or injected, or that comes into contact with the skin or eyes’

  7. Allergic disease spectrum • Food allergy • Eczema • Asthma • Allergic rhinitis • Drug allergy

  8. Allergy – a public health problem • Prevalence of asthma & hayfever have increased over the last 20 years (3 - 8.2% and 5.8 - 20% respectively) Upton, BMJ 2000 • 12 million people per year may seektreatment for allergy • Children: 20.4% asthma; 18.2% hayfever; 47% 1 or more current symptoms (ISAAC study, 1999)

  9. Epidemiology of Food Allergy • Peanut allergy (3 yr olds) • Sensitisation: threefold increase 1989-1994-6 from 1.1-3.3.% • Doubling of reactivity from 0.5-1% JACI 2001;107:S231 • Admission rates Anaphylaxis risen 7-fold; 5/million 1990/1- 36 2003/4 Food allergy risen 7-fold; 16 - 107/million Urticaria doubled; 20 – 44/million – especially children

  10. Allergy – a primary care problem • 6% of GP consultations • Primary Care Prescribing • 1991-2004: community prescriptions increased • Nasal allergy - by 60% (to 4.5 million) • Anaphylaxis – 12 fold (to 124,000) • Ocular allergy – by 50% (to 1.4 million) • Costs NHS £900 million pa • Excludes costs of A&E attendances, outpatient consultations, hospital treatment BSACI, London, commissioned study, 2002

  11. Why should children with suspected allergy be tested? • May be lifelong • Specific treatment • Early treatment may influence severity • May be life threatening • Associated with poor quality of life • May herald other allergic diseases • ‘Allergic March’

  12. Eczema Asthma

  13. Food poisoning Toxic IgE Adverse Reaction to Food Allergy Immune mediated Non IgE Non toxic Enzymatic Non-immune mediated Pharmacological Aversion Undefined Adverse Reactions to Food

  14. Non-immune ARF • ‘Undefined’ • Mechanism unknown • Food additives, preservatives, colourings • ‘Generally Recognised as Safe products [GRAS] • Sulphites, nitrites, nitrates, MSG • Urticaria, rhinitis, asthma, migraine

  15. Food Allergy - Definition • An immune-mediated adverse reaction to food that occurs in genetically predisposed individuals • IgE urticaria; oral allergy; anaphylaxis • Non IgE Cell-mediated; mixed • Consistent • Reproducible

  16. How does the immune system malfunction in food allergies? Step 1: Sensitisation IgE production B cell Th2-biased cytokine production Th cell Allergen Exposure Processing Presentation

  17. Step 2: Activation - Effector Phase Vasodilatation Pain Cell recruitment Mucosal oedema Immune Modulation IgE induction Tissue remodelling Smooth muscle contraction Peristalsis

  18. Clinical Manifestations: Immediate • Erythema • Pruritus (generalised) • Urticaria • Angioedema • Rhinitis • Laryngeal oedema • Asthma • GI upset

  19. Symptoms • Immediate • Delayed type / Chronic • Inflammation • Abdominal pain • Altered gut function • Poor asthma control

  20. Clinical Manifestations: non IgE-mediated reactions Delayed type • SKIN: eczema flares • GUT: • Mucousy / bloody stools in an infant • Chronic diarrhoea, vomiting • Failure to thrive • Malabsorption • Dysphagia, abdominal pain • Proctitis / dietary protein enteropathy / eosinophilic gastroenteropathies

  21. What foods? Cow’s milk, Egg white, Soybean, Wheat, Peanut, Tree nuts, Fish & Shellfish account for >90% reactions

  22. Red flag features of allergy • Clear temporal relationship with trigger • Consistency of reaction • Trigger – likely allergen • Timing – within 2 hours of ingestion • ‘Typical’ clinical symptoms • Other features of atopy • Family history of atopy

  23. Example 1 • 3½ year old girl • Eczema since 1 year age • Ate 1 salted peanut 18 months ago • Developed • lip swelling & wheeze • No rash, GI upset or respiratory distress • Mum – asthma & hayfever

  24. Example 2 • 11 year old girl • No other atopic disease • Xmas - ate raisin from bowl of mixed nuts • Developed lip swelling & local urticaria 5 – 10 minutes later • Settled with oral piriton • Father – eczema & occasional ‘wheeze’

  25. What’s the diagnosis? • Peanut allergy • Tree-nut allergy • ‘Other’

  26. Diagnostic Adjuncts • Skin Prick Testing • Cheap • Painless • Fast • Sensitive & specific • Specific IgE measurement • Blood test • Hx of anaphylaxis • Recent antihistamine use • Widespread eczematous skin

  27. Skin prick test

  28. Results - cases • Case 1: • SPT peanut 6 mm • SPT tree nut panel negative • Specific IgE peanut 5.6 kU/L • Case 2: • SPT peanut 6 mm • SPT brazil nut 4 mm; remainder negative • Specific IgE peanut 90 kU/L; brazil 2.4 kU/L

  29. Interpretation • Case 1: peanut allergic • Case 2: peanut & tree-nut allergic • SPT weal size or Specific IgE level • No relation with severity of reaction

  30. Red flag features of management • Awareness • Avoidance • Asthma control • Anti-histamine • Adrenaline autoinjector

  31. Management • AWARENESS • Parents • Wider family • School • Physician • GETTING THE DIAGNOSIS RIGHT

  32. Management • AVOIDANCE OF ALLERGENS

  33. Management • AVOIDANCE

  34. Management • ASTHMA CONTROL

  35. Management • ANTI-HISTAMINE

  36. Management • ADRENALINE (EPINEPHRINE)

  37. Who should get an epipen?

  38. Lethal anaphylaxis • Uncommon • 0.65-2% of severe anaphylaxis ‘KISS OF DEATH FOR NUT ALLERGY GIRL’ A teenage girl with an extreme allergy has died after kissing her boyfriend who had eaten a peanut-butter sandwich hours earlier. Christina Desforges, 15, from Saguenay, Canada, went into anaphylactic shock. She was given an adrenalin shot and taken to hospital but died four days later from acute respiratory failure. Doctors said that a nut allergy brought on by the kiss was the cause of death. The boy, who has not been named, had minute traces of peanut on his lips. Nov ‘05

  39. Lethal anaphylaxis: ‘predictable’ risk factors • Peanut / treenuts • Asthma • Adolescents / young adults

  40. Lethal anaphylaxis: ‘unpredictable’ risk factors • Severity history of previous food reaction • Pumphrey • 22% of fatal cases had had previous severe reaction

  41. Severity History Macdougall et al, 2002, Arch Dis Child

  42. Red flag features of epipen prescription • Indicated: • History of severe reaction • Reactions becoming more severe • Asthma (requiring inhaled steroid use) • Consider: • If low dose (trace) exposure • At a distance from nearest medical facility • If having difficulty avoiding • If parents anxious +

  43. Prognosis

  44. IgE mediated reactions • Resolve: Cow’s milk, Egg, Soya, Wheat • By 5 years age, tolerance in • 85% of CMA children • 66% of egg allergic children • Persist: Peanut, Tree nut, Fish & Shellfish • However, around 20% of PA will resolve • Youngest patients • Low specific IgE • Mild reaction at presentation

  45. Frequently Asked Questions

  46. Is a food allergy causing my child’s hyperactivity? • Number of ways in which food could affect cognition & behaviour in children • Mechanism not ‘allergy’ • Some benefit in ‘extreme’ subgroups • Complex behavioural problems +/- neurological deficits • Possibility that food additives may have a pervasive effect across the population

  47. ‘Food Allergy’ & behaviour • Bateman study • 277 children • Hyperactivity / atopy • Randomised, placebo-control, Double blind, cross-over: food colouring & Na benzoate • Assessed weekly by psychologists; parents daily • Parental ratings associated with dietary additives • No association with atopy

  48. ‘Food Allergy’ & behaviour • Confirmed in follow on study • 3-year old children (n=153) • 8/9 year old children (n=144) • Within subject crossover – 2 active mixes; 1 placebo (3 year olds x2 56g sweets; 8 yr olds 2-4 bags sweets / day • Global Hyperactivity Aggregate increased in both age groups with active mix

  49. My child has egg allergy – should he have the MMR? • YES • Unless • Immunocompromised • Had an anaphylactic reaction to previous MMR • Had an anaphylactic reaction to gelatin / neomycin • Close observation if • Previous acute severe reaction to egg • Current active, chronic asthma

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