Allergic Rhinitis — Causes, Symptoms & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

Allergic rhinitis is a chronic IgE-mediated inflammatory condition of the nasal mucosa triggered by inhaled allergens, affecting 10-30% of adults and up to 40% of children worldwide — approximately 400 million people. It is classified as seasonal (triggered by pollen — trees in spring, grasses in summer, moulds in autumn) or perennial (year-round — caused by house dust mites, pet dander, cockroach allergens, indoor moulds). Many patients have both types. Allergic rhinitis is strongly associated with asthma (30-40% of AR patients have asthma), allergic conjunctivitis, atopic dermatitis, and sinusitis — collectively termed the 'atopic march.' Despite being considered a minor condition, severe allergic rhinitis impairs sleep, work and school performance, and quality of life substantially. The condition carries a significant economic burden through billions of hours of lost productivity annually. Early allergen identification and stepwise treatment substantially improve patient quality of life and reduce reliance on rescue medications.

Allergic rhinitis results from type I (immediate) hypersensitivity: prior sensitisation to an allergen causes IgE production, which binds mast cells in nasal mucosa. Re-exposure triggers mast cell degranulation releasing histamine, prostaglandins, leukotrienes, and cytokines — causing immediate (within minutes) and late-phase (4-6 hours later) nasal inflammatory responses. Common allergens: outdoor — grass pollens (Timothy, ryegrass), tree pollens (birch, alder, hazel), weed pollens (Parietaria, ragweed), Alternaria and Cladosporium moulds; indoor — house dust mite (Dermatophagoides pteronyssinus), cat and dog dander, cockroach allergens, Aspergillus mould. Risk factors: personal or family history of atopy, early exposure to tobacco smoke, urban living, and reduced childhood microbial exposure (hygiene hypothesis).

The four cardinal symptoms of allergic rhinitis form the mnemonic NASC: Nasal discharge (anterior rhinorrhoea — clear, watery), nasal Airflow obstruction (congestion), nasal itching (pruritus — leading to 'allergic salute' — rubbing nose upward), and Sneezing (often in paroxysms). Additional features: postnasal drip causing throat clearing and cough; hyposmia (reduced smell); palatal and ocular itching; facial pressure and headache from secondary sinusitis; and 'allergic shiners' (dark periorbital circles from chronic venous congestion). Severity is classified by ARIA criteria: intermittent (less than 4 days per week or less than 4 weeks) vs persistent; and mild vs moderate-severe (based on impact on daily activities, sleep, and work). Perennial rhinitis often causes predominantly nasal congestion with less sneezing than seasonal disease.

Diagnosis is clinical, based on characteristic symptoms with allergen correlation. Confirmation of sensitisation guides treatment: skin prick testing (SPT) is the gold standard — 15-minute test placing allergen extracts on the skin with a lancet, measuring wheal diameter; a wheal 3 mm or more larger than the negative control is positive. Specific IgE blood testing (RAST, ImmunoCAP) measures circulating allergen-specific IgE and is useful when SPT is impractical (dermatographism, widespread eczema, antihistamine use). Component-resolved diagnostics identify specific allergenic proteins (e.g., Phl p 5 for timothy grass, Bet v 1 for birch) to guide immunotherapy candidacy. Nasal endoscopy excludes structural causes (polyps, deviated septum). Differential diagnoses include non-allergic rhinitis (vasomotor, occupational, hormonal — no allergen sensitisation), nasal polyposis, and rhinitis medicamentosa (rebound from decongestant overuse).

Allergen avoidance reduces trigger exposure: impermeable mattress/pillow covers and weekly hot-washing of bedding (above 60°C) for dust mite allergy; HEPA air filters and pet restriction (not guaranteed effective) for pet allergens; daily pollen count monitoring and keeping windows closed during high pollen periods. Pharmacotherapy: intranasal corticosteroids (INS — mometasone, fluticasone furoate, budesonide) are the most effective monotherapy for all symptoms, working within hours to days — use daily during pollen season or year-round; oral second-generation antihistamines (cetirizine, loratadine, fexofenadine, bilastine) are effective for sneezing, itching, and rhinorrhoea but less effective for congestion — no sedation with modern antihistamines; intranasal antihistamines (azelastine) provide faster onset than oral formulations; oral decongestants (pseudoephedrine) provide short-term congestion relief; nasal decongestant sprays (oxymetazoline) for maximum 5-7 days (risk of rebound rhinitis). Allergen immunotherapy (AIT): subcutaneous (SCIT — weekly injections for 3-5 years) or sublingual (SLIT — daily drops or tablets for 3-5 years) — the only treatment modifying the underlying allergic disease, inducing long-term tolerance and preventing new sensitisations; most effective for grass pollen, house dust mite, and cat allergy.

Poorly controlled or untreated allergic rhinitis leads to significant health consequences beyond nasal symptoms. Chronic nasal congestion promotes mouth breathing, which causes disrupted sleep, snoring, and worsening of obstructive sleep apnoea — resulting in daytime fatigue, cognitive impairment, and poor academic or work performance; studies show a 6-fold increase in cognitive dysfunction during pollen season in patients with uncontrolled seasonal rhinitis. Nasal polyps develop in approximately 25% of patients with chronic allergic rhinitis, causing complete nasal obstruction and anosmia requiring endoscopic sinus surgery. Untreated rhinitis is a major risk factor for developing asthma — approximately 20-40% of patients with allergic rhinitis will develop asthma over their lifetime, particularly if rhinitis is untreated. Recurrent secondary sinusitis (bacterial superinfection of inflamed sinuses) causes significant pain and antibiotic use. Eustachian tube dysfunction leads to chronic otitis media with effusion (glue ear) and hearing loss, particularly in children. Adenoidal hypertrophy from chronic nasal inflammation causes further airway obstruction in children.

Monitor local pollen counts (available through weather apps) and limit outdoor exposure on high-count days, especially in the morning when pollen is densest. Shower and wash hair after outdoor exposure during pollen season. Wear wraparound sunglasses to reduce eye allergen contact. Avoid outdoor exercise on high pollen days or exercise indoors. For dust mite allergy: maintain bedroom humidity below 50%, vacuum with HEPA-filter machines, remove carpets where possible, and use allergen-proof bedding encasements. Avoid tobacco smoke exposure — it significantly worsens allergic rhinitis and increases asthma risk. Nasal saline irrigation (neti pot or spray) clears allergens from nasal mucosa and improves mucociliary clearance. Consider allergen immunotherapy for those with moderate-severe disease inadequately controlled by medication — it offers disease modification rather than just symptom control.

Consult a GP if nasal allergy symptoms are significantly affecting your sleep, work, or daily activities, or if over-the-counter antihistamines are providing inadequate relief. Seek referral to an allergist or ENT specialist if symptoms persist year-round and are severe, if asthma coexists with rhinitis (united airway disease), if you are considering allergen immunotherapy, or if there is diagnostic uncertainty about the allergen trigger. Seek urgent assessment for severe facial swelling, high fever, unilateral symptoms or blood-stained discharge (possible sinus infection or rarely malignancy), or sudden complete loss of smell. Children with perennial symptoms and persistent nasal obstruction should be evaluated for adenoidal hypertrophy and potential impact on speech and hearing.