Allergic Rhinitis Flashcards
Definition of Allergic Rhinitis
- lgE mediated (type I hypersensitivity reaction) inflammation of nasal mucosa after allergen mucosa
- A/w personal and family history of atopy (eczema/atopic dermatitis, asthma, allergic conjunctivitis)
- Bilateral involvement
Pathogenesis of allergic rhinitis
Starts with allergen exposure and sensitisation
lgE mediated (type I hypersensitivity reaction)
- Early phase: mast cells and basophils degranulate -> releasing histamine -> vasodilation and mucus production:
- rhinorrhea
- nasal congestion
- nasal itching
- sneezing - Late phase: cellular (eosinophils, lymphocytes, monocytes) infiltration -> remodelling
Triggers of allergic rhinitis
Aeroallergens:
Any airborne substance that can result in an IgE-mediated allergic response
- perennial allergens (experience symptoms year-round): dust mites*, cat and dog dander and cockroach
- tree, grass, and weed pollen
Clinical features of allergic rhinitis
2/4 cardinal symptoms:
- Rhinorrhea
- Nasal congestion
- Nasal itching
- Sneezing
* reversible spontaneously or with treatment
+/- Ocular symptoms:
- itchy eyes
- red eyes
- tearing
Signs in allergic rhinitis
*bilateral involvement
- Allergic salute
- characteristic & habitual gesture of wiping/rubbing the nose in an upwards or transverse manner with the fingers, palm, or back of the hand - Supratip crease
- Allergic shiners
- infraorbital edema and darkening due to venous congestion secondary to impeded blood flow through edematous nasal mucosa - Dennie-Morgan fold/line
- fold or line in the skin below the lower eyelid - Geographic tongue
- inflammatory but harmless condition affecting the surface of the tongue
- Patches on the surface of the tongue are missing papillae
- Patches are smooth and red, often with slightly raised borders - Cobblestone pharynx
- inflamed tissue in the back of your throat that looks bumpy - Pale and edematous nasal mucosa and inferior turbinate
Complications of allergic rhinitis
Sinusitis
Anosmia
Nasal polyps
Classification of allergic rhinitis
- Duration: intermittent or persistent
- Severity of symptoms and QOL: Mild or moderate
Intermittent
< 4 days/week OR < 4 weeks
Persistent
> 4 days/week AND > 4 weeks
Mild
- Normal sleep
- Normal daily activities, sport and leisure
- Normal work and school
- No troublesome symptoms
Moderate-Severe (≥1 item(s))
- Abnormal sleep
- Impaired daily activities, sport or leisure
- Problems at work or school
- Troublesome symptoms
Diagnosis of allergic rhinitis involves
- Hallmark symptoms, history suggesting atopy
- PE findings
- Allergy testing
Investigations for allergic rhinitis
Allergy testing is unnecessary in patients with clear history of symptoms triggered by specific allergens
- Skin prick test (in vivo)**
- Serum specific IgE test (in vitro)**
- Intradermal testing (in vivo)
- End-organ provocation testing (in vivo)
- Patch test (in vivo)
How does skin prick test work?
Make markings using pen, apply allergens (suspended in normal saline), prick skin for allergens to enter
+ve control: Histamine
-ve control: Normal saline
+ve result: Wheal ≥ 3mm compared to -ve control
*Faster (15 min) and cheaper
*Indirect measure of cutaneous mast cell reactivity due to presence of specific lgE
Absolute C/I to skin prick testing
- On beta-blockers (Adrenaline not able to work on beta receptors to cause bronchodilation during anaphylaxis)
- Recent anaphylaxis
- Allergy to peanut (May cause anaphylaxis)
- Extensive skin disease (E.g. eczema known to ↓ skin reactivity to histamine)
- Taken anti-histamines in past 3-5 days (yield false +ve results)
- Pregnant
- Dermatographism
- Asthma (Poor control)
- No clear skin
Relative C/I to skin prick testing
Too old or too young (too early for kids <5yo as immune system still developing)
Serum-specific IgE antibody test
- Detects amount of IgE that reacts specifically with allergen
- Gold standard, highly specific, quantitative and reflects severity of allergy
- eg. Radioallergosorbent test (RAST)
Management of allergic rhinitis
- Patient education
- increase patient compliance - Allergen identification and avoidance
- environmental control - Pharmacotherapy
- Immunotherapy
- Surgical
- Radiofrequency ablation of inferior turbinates (LA)
- Inferior turbinate reduction (GA)
- Septoplasty (GA)
Pharmacotherapy for allergic rhinitis
- Oral anti-histamines
- Topical nasal decongestants
- Limit use to at most 5-7 days to prevent rhinitis medicamentosa - Nasal irrigation (To improve mucociliary clearance)
- Intranasal steroid spray
- Fluticasone / Mometasone
- improvement seen 2 weeks later
- maintenance therapy - Cromolyn sodium (Mast cell stabiliser)
Immunotherapy for allergic rhinitis
- Gradual exposure of patient to doses of allergen extract
- In the long term (3 years), this induces changes in the immune system which modifies its response to the specific allergen
- Subcutaneous injections or sublingual table/spray
Indications:
- Failed Conservative
- Failed Medical
- Severe Allergies
Side Effects:
- Rashes
- Chest Tightness
- Throat Tightness
- Eyelid swellings
How is food allergy a/w allergic rhinitis?
- Peanut, milk, egg allergies predispose to development of allergic rhinitis and asthma
- Patients with multiple food allergies are also at increased risk of developing AR and asthma
- AR more frequently associated with a secondary rather than a primary food disorder
-> secondary mild food allergy aka oral allergy syndrome
Food allergic reaction
Immediate (IgE mediated) v.s. delayed (non-IgE mediated)
Presentations of food allergy
AR
Rhinosinusitis
Recurrent URTI
Chronic postnasal drip
Disturbing phlegm in throat
Chronic cough
Headache/ Facial pain/ Migraine
Eczema
Asthma
IBS
Types of Hypersensitivity reactions (Gell and Coomb’s classification)
I: Immediate (IgE)
II: Cytotoxic (IgG or IgM + Complement)
III: Immune complex reaction (IgG or IgM complement)
IV: Cell mediated, delayed hypersensitivity (Sensitized Lymphocytes)
Clinical features of IgE-mediated food allergy -> histamine release
- <5% of food allergic reactions
Immediate, acute onset of symptoms
Urticaria
Angioedema
Abdominal cramps, diarrhoea
Asthma
Anaphylactic shock, death
Clinical features of non-IgE mediated/delayed food allergy
- > 95% of food allergic reactions
Delayed reaction (hours to days) - Type 3 hypersensitivity
- Exposure dependant
- Masking phenomenon present → symptoms improve or disappear with ingestion of same food
- Affects multiple organ systems
- Associated with eczema
How to diagnose non-IgE, delayed food allergic?
Diet elimination
Oral challenge food test
Intradermal progressive dilution food test
Management of food allergy
IPDFT/ Elimination diet
Avoidance
Rotation diet
Food neutralizing injections/ Sublingual drops
Pharmacotherapy
