Allergy rhinitis

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Allergic Rhinitis (AR)

Definition

Allergic rhinitis is an IgE-mediated inflammatory disease of the nasal mucosa triggered by inhaled allergens. It is characterized by sneezing, nasal itching, watery rhinorrhea, and nasal congestion. It is the sixth most common chronic illness in the United States, affecting 10-20% of the adult population in the US and Europe, with a similar prevalence in children.

Murray & Nadel's Textbook of Respiratory Medicine, p. 1610

Classification

AR is classified along two axes:

By duration:

Intermittent - symptoms fewer than 4 days/week OR fewer than 4 weeks total
Persistent - symptoms more than 4 days/week AND more than 4 weeks total

By severity:

Mild - normal sleep, no impairment of daily activities
Moderate-Severe - sleep disturbance, impaired work/school, or troublesome symptoms

This ARIA (Allergic Rhinitis and its Impact on Asthma) classification guides treatment decisions.

Common Allergens

Type	Examples
Seasonal	Tree pollen, grass pollen, weed/ragweed pollen
Perennial	House dust mites, pet dander (cat, dog), cockroach
Occupational	Flour dust, latex, animal proteins

Pathophysiology

AR involves two distinct immunological phases:

Early Phase (within minutes of exposure)

Inhaled allergen binds to IgE antibodies on the surface of mast cells and basophils
Cross-linking of IgE antibodies triggers mast cell degranulation
Release of preformed mediators - primarily histamine, plus tryptase
De novo synthesis of leukotrienes
Result: marked tissue edema, mucus secretion - presenting as rhinorrhea, nasal obstruction, and sneezing

Late Phase (4-8 hours after exposure)

Chemoattractants and adhesion molecules recruit leukocytes, eosinophils, basophils, CD4+ lymphocytes, and monocytes
A second wave of inflammatory mediators is released
Nasal congestion dominates
Repeated allergen exposure leads to "priming" - amplification of the mucosal immune response
Murray & Nadel's Textbook of Respiratory Medicine, p. 1610

Clinical Features

Cardinal symptoms (the "SNEEZE" cluster):

Sneezing (often paroxysmal)
Nasal itching
Watery rhinorrhea
Nasal congestion/obstruction
Eye symptoms (itching, tearing) - particularly in seasonal AR

Physical examination signs:

Allergic salute - transverse nasal crease from repeated upward wiping of the nose
Allergic shiners - dark discoloration under the eyes (venous congestion)
Dennie-Morgan lines - extra infraorbital skin folds
Pale or bluish nasal mucosa with swollen, boggy turbinates
Cobblestoning of the posterior pharynx
Scott-Brown's Otorhinolaryngology, p. 287

Differential Diagnosis

Category	Examples
Allergic	Seasonal AR, Perennial AR
Inflammatory	Viral rhinitis, NARES (Non-allergic rhinitis with eosinophilia), chronic sinusitis
Hormonal	Pregnancy rhinitis, hypothyroidism
Rhinitis medicamentosa	Topical decongestant overuse, cocaine, antihypertensives
Vasomotor	Cold air-induced, irritant-induced (smoke), gustatory
Anatomic	Septal deviation, foreign body, CSF leak, nasal polyps

Goldman-Cecil Medicine, p. 4167

Diagnosis

History: Temporal pattern (seasonal vs. perennial), occupational exposure, family history of atopy.

Allergy testing:

Skin prick test (SPT): Gold standard - epicutaneous application of allergen extracts. Fast, inexpensive. Carry a small risk of anaphylaxis - epinephrine must be available.
Intradermal testing: More sensitive than SPT but less specific.
Serum-specific IgE (ImmunoCAP/RAST): Has largely replaced older radioallergosorbent tests. Similar sensitivity to skin testing. Preferred when skin testing is not feasible (e.g., severe eczema, inability to stop antihistamines).

Treatment

Three pillars: allergen avoidance, pharmacotherapy, and immunotherapy.

1. Allergen Avoidance

Use allergen-impermeable mattress/pillow encasements for dust mite
Remove pets from bedroom or home
Check local pollen counts (seasonal AR) and limit outdoor exposure on high-pollen days
HEPA filters for indoor allergens

2. Pharmacotherapy

Drug Class	Examples	Best For	Notes
Intranasal corticosteroids (INS)	Fluticasone, mometasone, budesonide	Perennial, moderate-severe AR; first-line	Most effective single agent; address congestion, rhinorrhea, sneezing
2nd-gen oral antihistamines	Cetirizine 10 mg, levocetirizine 5 mg, fexofenadine 180 mg, desloratadine 5 mg, loratadine 10 mg	Mild, intermittent/seasonal AR	Once-daily, non-sedating; superior to 1st-gen
Intranasal antihistamines	Azelastine, olopatadine	Add-on to INS if antihistamine needed	Preferred over oral antihistamines when combining with INS
Leukotriene receptor antagonists	Montelukast	Adjunct therapy	Less effective than INS alone; useful when asthma coexists
Intranasal decongestants	Oxymetazoline	Short-term only (max 3-5 days)	Risk of rhinitis medicamentosa with prolonged use
Oral decongestants	Pseudoephedrine	Congestion dominant	Avoid in hypertension, BPH
Saline irrigation	Isotonic or hypertonic saline	Adjunct	Modest benefit; improves mucociliary clearance, reduces medication need
Mast cell stabilizers	Intranasal cromolyn	Prevention (seasonal)	Requires 4x/day use; best started before season

Key treatment algorithm:

Mild intermittent: oral 2nd-generation antihistamine
Moderate-severe or persistent: intranasal corticosteroid (± antihistamine if needed; prefer intranasal form)
If antihistamine + INS needed: intranasal antihistamine + INS is preferred over oral antihistamine + INS

3. Immunotherapy (Disease-Modifying)

Immunotherapy is the only treatment that modifies the natural history of AR rather than just controlling symptoms.

Subcutaneous immunotherapy (SCIT):

Once- or twice-weekly subcutaneous allergen injections with dose escalation
Most studied approach; most commonly used in the US
Course: 2-3 years

Sublingual immunotherapy (SLIT):

Can be administered at home; avoids injections
FDA-approved products:
- Grastek (timothy grass pollen) - ALK-Abelló
- Oralair (5-grass pollen mix) - Stallergenes
- Odactra (dust mites) - ALK-Abelló
- Ragwitek (short ragweed) - ALK-Abelló
Course: 2-3 years

Mechanism of immunotherapy:

Shifts the immune response from Th2 (allergic) to Th1
Induces T-regulatory cells and IL-10/TGF-beta production
Reduces IgE and increases blocking IgG4 antibodies
Results in long-term tolerance to allergens
Murray & Nadel's Textbook of Respiratory Medicine, p. 1610

Comorbidities and Complications

The Unified Airway

AR and asthma share pathophysiology. 80% of patients with allergic asthma also have AR. AR is an independent risk factor for developing asthma. Guidelines recommend screening all patients with persistent AR for asthma.

Segmental bronchial allergen challenge in AR/asthma patients produces inflammation in both the nose AND bronchi
Treatment with intranasal corticosteroids reduces both nasal and bronchial hyperreactivity

Other Comorbidities

Chronic rhinosinusitis (CRS) - frequently coexists; evaluate and treat AR in any child with CRS
Otitis media with effusion - Eustachian tube dysfunction from nasopharyngeal inflammation
Sleep-disordered breathing / OSA - nasal obstruction contributes
Conjunctivitis - seasonal AR commonly associated
Anosmia - from chronic mucosal edema

Hygiene Hypothesis

The rising incidence of AR over the past 3 decades is partly explained by the hygiene hypothesis: reduced early childhood exposure to microbial antigens leads to inadequate immune system maturation, resulting in exaggerated Th2 responses to environmental allergens. Early microbial exposure may protect not only against atopic disease but also autoimmune conditions.

Key Pearls

AR costs ~$1,500/patient/year in direct healthcare costs; 3.5 million workdays are lost annually in the US
1st-generation antihistamines (diphenhydramine, chlorphenamine) are sedating and impair cognitive performance - avoid for driving or school
Rhinitis medicamentosa from decongestant overuse can mimic and worsen AR
ARIA guidelines (updated 2017) replaced seasonal/perennial classification with intermittent/persistent + mild/moderate-severe severity grading
Montelukast carries an FDA black box warning for neuropsychiatric effects (anxiety, depression, suicidality) - use cautiously

Sources: Murray & Nadel's Textbook of Respiratory Medicine; Goldman-Cecil Medicine; Cummings Otolaryngology; Scott-Brown's Otorhinolaryngology

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