Dr Jeanne Powell

ALLERGY IN GENERAL PRACTICE

“I think I must be allergic to something, Doctor”

THE ESSENTIAL GP TOOL KIT

Gell and Coombs ClassificationTYPE I IgE mediated

Allergy to protein

TYPE II IgG response

Cell lysis

TYPE III IgG or IgM mediated

Immune complex deposition

TYPE IV T cell mediated

Delayed hypersensitivity

IgE allergic hyperresponsiveness

Interrelationships between Allergy and Hyperresponsiveness

IgE sensitisationHyperresponsiveness

Non-IgE hyperresponsiveness

‘Latent’ allergy clinical tolerance

AsthmaRhinitis/Conjunctivitis

Food/drug reactionUrticaria/angioedema

Anaphylaxis

GRADE Brown et al 2006

1 MILD Skin and subcutaneous tissues only: Generalised erythema, urticaria, periorbital oedema or angioedema

2 MODERATE Respiratory, cardiovascular or gastrointestinal involvement: Dyspnoea, stridor, hoarseness, wheeze Nausea, vomiting Dizziness (presyncope), diaphoresis Chest or throat tightness, abdominal pain

3 SEVERE Hypoxia, hypotension or neurological compromise: Cyanosis or SpO2≤92%

Systolic blood pressure<90mmHg in adults Confusion, collapse, loss of consciousness

Grading system for Anaphylaxis

Management of Anaphylaxis

RESCUE KIT:

MILD: Anti-histamine high dose

MODERATE: ADD Soluble prednisolone 30mg (0.5mg/kg)

SEVERE: ADD Adrenaline auto injector300mcg over 30kg150mcg 15-30kg

PRACTICAL ALLERGY

Allergy in 10 minutesDETECTIVE WORK

• Presenting episode vs Previous episodes

• Consistent trigger (<4 hours) or pattern to episodes

• Co-factors - exercise/alcohol/NSAIDS/intercurrent illness

• Dose of allergen vs severity of reaction

• Atopic medical history - CONCURRENT ASTHMA

Top 8 Food allergensPeanuts

Fish

Treenuts

Eggs

Dairy

Shellfish

Soy

Wheat

Case Study• 35 year old secretary• Itchy rash – moves about over torso and limbs• Increasing in frequency/severity for 4 weeks• Has been to A&E twice with facial swelling • Treated with steroids - briefly successful• Taking OTC cetirizine PRN, then daily• Had an infected insect bite about a month ago• Wants to find out what to what she is allergic

Urticaria in 10 minutes

– Lesions itchy NOT painful/bruising– Pattern/duration– Consistent link with particular trigger– Foods: usually present within 4 hours– Relationship to temperature/pressure/exercise– Associated swelling/systemic symptoms– Associated asthma / atopy / AI disease– Family history (HAE/thyroid/AI)

Examination

• Presence of:– Thyromegaly?– Dermographism?

• Examine lesions if present

Urticaria with/without Angioedema

Idiopathic MAJORITYPhysical Dermographism

Stress, Viral infectionsCholinergicCold/aquagenic/solar/vibratoryDelayed Pressure Urticaria

Allergic Food, Venom, Latex, Contact urticaria

Drug Induced Opiates, NSAIDs, Antibiotics, Statins, Anti-depressants

Urticarial Vasculitis InfectionDrugs : penicillin, allopurinol,

quinolones, carbemazepineAutoimmune, paraproteinaemia, malignancy

Investigations

• May not need any!• If dermographic- SPT may not be helpful• Consider TFT, TPO, ANA, C3 and C4

Have the explanatory chat

This really does save time in the long run!

Treatment

BEGIN REGULAR:• Fexofenadine 180mg up to bd• ADD Ranitidine 150mg bd• ADD Montelukast 10mg nocte

RESCUE:• Chlorpheniramine 8mg nocte or • Cetirizine/Loratadine 10mg bd PRN

Case Study • 55 year old pilot, 10 year history of:• 1 or 2 episodes/month of variable severity of

hives/lip swelling- settles with fexofenadine• 5 bad episodes of severe urticaria, swelling

and fainting, most whilst away in Wales• Routinely goes to the gym on most mornings• No foods avoided• Takes fexofenadine before flights to prevent

episodes

Wheat Dependent Exercise Induced Anaphylaxis

• Anaphylaxis dependent on combination of wheat dose and exercise within a 4 hour period

• Symptoms vary from urticaria through to severe anaphylaxis

• Positive Omega-5-Gliadin (Tri a 19)• Positive SPT to wheat hydrolysate• May have negative test to wheat and gluten

• Referral important – dietician/assessment• Prophylactic antihistamines

• 72 year old retired accountant• Hypertension for 6 years - on ramipril & statin• MI 1 year ago - on bisoprolol & aspirin since • Monthly facial swellings began 8 months ago• In the last month- 2 episodes of tongue

swelling overnight- Called ambulance• Rx prednisolone/AH and taken to A&E for obs.• Now carries adrenaline

Case Study

24%

8%

13%

2%

3%

1%

49%

ACE-I related angioedema

Other drug related angioedema

Allergic angioedema

Physical angioedema

Hereditary angioedema

Acquired angioedema

Idiopathic angioedema

384 patients RSCH 2003-09

Isolated Angioedema

Isolated Angioedema

Idiopathic Majority

Drugs Oestrogen, ARB, NSAID, Antibiotics, Statins

ACE-Inhibitors Not necessarily recently started

Allergic Food, Venom, Latex

Physical Delayed Pressure

Hereditary Angioedema usually presents before age 20

Acquired C1 esterase deficiency especially older age groups

Investigations

• IgE, SpIgE / Phadiotop – from history!• TFT/TPO /HR Ab*• Isolated Angiodema:

– C3, C4, C1 inhibitor– Immunoglobulins – Electrophoresis

TreatmentREGULAR DAILY• Anti-histamine- high dose H1 antagonist

– Cetirizine 10mg bd– OR Fexofenadine up to 180mg bd

• Add H2 receptor antagonist– Ranitidine 150mg bd

• Add Leukotriene antagonist—Montelukast 10mg nocte

• Add other drugs –Second anti-histamine (Tranexamic acid, steroids, azathioprine)

Rescue

• Mild swelling (outside teeth)– Piriton 8mg/cetirizine 10-20mg

• Moderate swelling (inside mouth)– ADD Soluble prednisolone 30mg

• Severe swelling (affecting throat)– ADD Adrenaline auto injector

Case Study

• 16 year old boy, GCSE year

• Hay fever from late spring to summer

• Itchy eyes, sneezing and stuffy nose

• Blocked ears and itchy palate

• Takes OTC anti-histamines PRN

• Wants to know if there is a cure as fed up!

Hay fever

• Spring: Tree pollen (January to May)

• Summer: Grass pollen (June)

• Autumn: Weed pollen (September)

• Perennial: Animal danderMould spores House Dust Mite

Investigations

• No testing really needed unless considering referral for Sub Lingual Immunotherapy (SLIT)

• Skin prick testing ideal

• Sp IgE also useful– Phadiotop : house dust mite, grass and tree

pollen, cat dander

Treatment: Hay fever• Start daily 2/52 prior to earliest symptoms• ‘Itchy –Sneezies’: Antihistamines up to bd• Nasal congestion: Intranasal Steroids up to

bd• Fluticasone nasules 6 drops each nostril bd for 2 weeks• INS spray bd, reducing to daily when possible

• Eyes: Na cromoglycate• ADD Montelukast 10mg nocte• ADD Rescue steroids 5 days• REFER SLIT (season on maximal Rx

Case Study

• 31 year old teacher• Itchy mouth and lips after eating apple, peach,

cherry, raw carrot and hazelnuts• Apple pie and tinned peaches - no symptoms• Peeling potatoes- itchy eyes and sneezing• Hay fever in May• Mild asthma and eczema

Oral Allergy Syndrome

• Food cross reactions to Silver Birch pollen

• Associated hay fever in May

• Heat labile proteins primarily limited to pulp of fruit

• Cooked and processed foods often tolerated

• Common fruit & vegetable allergy in Northern Europe

Examples of cross reacting foods:Birch Pollen

ROSE FAMILY:• Apple• Pear• Cherry• Peach• Nectarine• Plum• Honey

• Hazelnut• Brazil nut• Almond• Peanut• Walnut

• Carrot• Potato• Parsnip• Onion• Tomato• Celery• Spinach• Fennel

Grass Pollen

• Melon• Orange• Tomato• Watermelon• Wheat• Swiss chard

Patients need only avoid foods causing symptoms (not all cross reacting foods)

Severe OAS (LTP Allergy)• Proteins stable to heat and digestion

• Primarily in peel of fruit or vegetable

• Reactions also to cooked and processed foods

• Often associated with severe and systemic reactions as well as OAS

• Commonly related to allergic reactions to fruit and vegetables in Southern Europe

Summary: Severe vs Mild OAS vs Latex

• Myriad of possible cross reactions are possible and so can be very difficult to discern

• Overall, I look for a pattern

• Consider: – Extent of food cross reactions

– Raw vs Cooked reactions

– Severity of reactions

– Associated allergens - pollens/latex

– Co-existing asthma

Skin Prick Testing

• Safe for airborne allergens

• Small risk of anaphylaxis for other tests

• Rapid result and highly acceptable test

• Not freely available in GP

Specific IgE Testing

• Looks for antibodies to specific allergenic protein extract so a safe test

• Grade 0 (negative) to Grade 6 (positive)BUT:• Sp IgE Sensitisation Clinical allergy• Strength of positive Clinical severity• False positives: Cross reacting proteins

Very high IgE levels (eczema)

Component Resolved Diagnosis

Allergenic Food Source

Allergenic Extract

Unique allergen molecules

Cross-reactive allergen molecules

Skin prick tests

Specific IgE

Component Resolved Diagnostics

CRD Testing for Nut Allergy

• Request Ara h2 and Ara h8

• If Ara h8 positive = Oral Allergy Syndrome and lower risk of severe systemic reaction

• If Ara h2 positive = True Nut Allergy likely and higher risk of severe systemic reaction

• AVOIDANCE IS STILL NEEDED• Affected by allergen load and patient factors

Case Study:

• 6 year old boy, new to area• Peanut butter at 2 years - facial swelling, hives

and vomiting• SPT positive to peanut, and brazil nut 2 years ago• Successfully avoided nuts since, carries piriton• Eczema as a baby, now has mild asthma• Referred to check if still allergic to nuts• Younger sibling aged 2 has never had nuts

Investigating Nut allergy

• Skin prick tests– Quick result, small risk anaphylaxis– >8mm - assumed allergic

• SpIgE:– Nut mix 1 (peanut, hazelnut, brazil, almond, coconut)

– Nut mix 2 (Cashew, pecan, pistacio, walnut)

– False positives and negatives– Severity can’t be inferred from results

Nut Allergy

• Spectrum of disease• 1 in 3 children may outgrow allergy• This more likely if allergy before age of 2 years• BUT some of these children redevelop allergy• Therefore regarded as an enduring allergy• Sibling risk 1:10 (Graduated skin challenge)• Peanut densensitisation subject of trials only

Case Study• 28 year old motorbike salesman for Europe

• Stung mid chest whilst out on motorbike

• Within minutes- metallic taste in mouth, chest pain and DIB- pulled into service station

• Collapsed - passing doctor treated him with adrenaline/steroids (!!)

• Previous stings: 8 years before and 2 months previously– Large local reaction only

Venom Allergy

• Hymenoptera : bee, wasp, hornet

• High risk occupations/hobbies

• Causes 20% of fatal anaphylaxis cases in UK

• Refer systemic reactions for consideration of VIT

• Bloods: Sp IgE bee/wasp venom and Serum tryptase

Venom Allergy

• Large Local Reactions:– Any swelling contiguous with sting– Treat with prednisolone

• Systemic Reactions:– Any symptoms occurring apart from sting– Adrenaline carriage mandatory– Venom immunotherapy ~3 years (95-98% success)

When to Refer

• Symptoms do not respond to treatment/avoidance

• Confirmed IgE mediated food allergy with asthma

• Tests are negative but a strong suspicion of allergy

• Anaphylaxis of uncertain cause

• Review of condition/for retesting/management

• Concern (doctor and/or patient!)

Useful Websites

• Advice leaflets:• www.patient.co.uk

• Anaphylaxis : • www.anaphylaxis.org• www.yellowcross.co.uk• www.jext.co.uk

•Guidelines:• BSACI/EAACI*

Any questions?

Thank you