EENT · PANCE / PANRE

Allergic Conjunctivitis

IgE-mediated bilateral ocular itching, redness, and watery discharge — frequently with allergic rhinitis.

Also known as: allergic conjunctivitis, seasonal allergic conjunctivitis, perennial allergic conjunctivitis, vernal keratoconjunctivitis, atopic keratoconjunctivitis

Overview

Bilateral IgE-mediated inflammation of the conjunctiva caused by environmental allergens. Forms: seasonal (SAC, pollen) and perennial (PAC, dust mite/animal/mold) — most common; vernal keratoconjunctivitis (VKC) — pediatric, atopic, severe with corneal involvement; atopic keratoconjunctivitis (AKC) — adult, chronic, sight-threatening; giant papillary conjunctivitis (GPC) — related to contact lenses or ocular prostheses.

Epidemiology

Affects 15-40% of the population in some form. Often coexists with allergic rhinitis, asthma, and eczema. VKC is most common in male children 5-15 in warm climates; AKC affects adults with atopic dermatitis.

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Risk factors

Personal or family history of atopy (asthma, eczema, food allergy, allergic rhinitis)
Exposure to seasonal allergens (pollen) or year-round allergens (dust mite, mold, pet dander)
Contact lens wear (GPC)
Warm dry climate (VKC)
Childhood (VKC)

Pathophysiology

Allergen exposure cross-links IgE bound to conjunctival mast cells, causing degranulation with histamine, tryptase, prostaglandins, and leukotrienes. Early phase: itching, tearing, redness within minutes. Late phase: eosinophil infiltrate hours later → chemosis and persistent symptoms. VKC and AKC have additional Th2-driven chronic inflammation with eosinophils.

Clinical presentation

Symptoms

BILATERAL itching — the hallmark; 'I want to rub my eyes constantly'
Watery or stringy mucoid discharge
Redness, burning, foreign body sensation
Eyelid swelling and chemosis
Concurrent nasal symptoms (sneezing, congestion) — allergic rhinoconjunctivitis
Triggered by pollens, animal dander, dust

Signs / physical exam

Diffuse conjunctival hyperemia and chemosis (clear gelatinous swelling)
Papillary reaction on tarsal conjunctiva (giant papillae in VKC, AKC, GPC)
Watery or ropy mucus discharge
Mild eyelid edema
Allergic shiners
VKC: limbal Horner-Trantas dots, shield ulcer on cornea — sight-threatening
AKC: lichenified eyelid skin, keratoconus, cataracts in chronic disease

Classic findings

Bilateral itching with chemosis and watery stringy discharge in an atopic patient.

Differential diagnosis

Viral conjunctivitis — Watery discharge, preauricular adenopathy, recent URI, follicular reaction; itching mild
Bacterial conjunctivitis — Purulent discharge, eyelids matted shut, no itching
Dry eye disease — Burning, foreign body sensation, worse end of day, fluorescein punctate staining, low tear film breakup time; artificial tears, cyclosporine
Blepharitis — Eyelid margin scaling, telangiectasias, crusting; lid hygiene
Contact dermatitis of eyelid — Erythema and scaling of lid skin, history of allergen exposure (cosmetics, drops); topical steroid to lid
Toxic conjunctivitis — Recent topical drop or preservative exposure; resolves with cessation
Giant papillary conjunctivitis (GPC) — Contact lens wearer with itching, mucus, large papillae on upper tarsus; lens hygiene change

Diagnostic workup

Labs

Clinical diagnosis based on history and exam
Allergy testing (skin prick or specific IgE) if persistent or trigger unclear
Conjunctival scraping rarely needed — would show eosinophils

Imaging

Slit-lamp examination for chemosis, papillae, and corneal involvement
Fluorescein staining if corneal symptoms — exclude shield ulcer or punctate keratitis

Diagnostic algorithm

Subtype	Population	Key Features	Risk
Seasonal allergic conjunctivitis (SAC)	Atopic, all ages	Pollen-triggered, itching, chemosis	Low — symptomatic
Perennial allergic conjunctivitis (PAC)	Year-round atopic	Dust mite/pet/mold-triggered	Low — symptomatic
Vernal keratoconjunctivitis (VKC)	Boys 5-15, warm climate	Cobblestone tarsal papillae, Horner-Trantas dots, shield ulcer	Sight-threatening (shield ulcer, keratoconus)
Atopic keratoconjunctivitis (AKC)	Adults with atopic dermatitis	Chronic, eyelid lichenification, corneal scarring	Sight-threatening; keratoconus, cataract
Giant papillary conjunctivitis (GPC)	Contact lens wearers	Itching, mucus, giant tarsal papillae	Lens intolerance

Subtypes of allergic conjunctivitis with distinguishing features and risk.

Treatment

First-line

Allergen avoidance — close windows during high pollen counts, wash hands and face after exposure, dust mite covers, pet dander measures
Cold compresses to reduce itching and swelling
Artificial tears (preservative-free preferred) to dilute and wash allergens
Topical ophthalmic antihistamine/mast cell stabilizer — olopatadine 0.1-0.7%, ketotifen 0.025%, alcaftadine, bepotastine — combined agents are first-line for moderate-severe disease
Topical mast cell stabilizer alone — cromolyn, lodoxamide, nedocromil — slower onset, useful prophylactically
Oral 2nd-generation antihistamine (loratadine, cetirizine, fexofenadine) if concurrent allergic rhinitis

Second-line / adjunct

Topical NSAIDs (ketorolac) — short-term symptom relief
Topical corticosteroids — short course (1-2 weeks) under ophthalmologist supervision for severe acute flares; monitor IOP and cataract formation
Topical calcineurin inhibitors (cyclosporine 0.05-0.1%, tacrolimus) — VKC/AKC and steroid-sparing chronic cases
Allergen immunotherapy (SCIT or SLIT) — particularly when concurrent allergic rhinitis warrants disease modification
Ophthalmology referral for VKC, AKC, shield ulcer, GPC unresponsive to lens change, or steroid dependence

Complications

Chronic eye rubbing → keratoconus (especially in VKC/AKC)
Corneal shield ulcer in VKC (sight-threatening)
Cataract and glaucoma from chronic topical steroid use
Secondary bacterial infection from rubbing
Reduced quality of life, sleep disruption, school/work impairment

PANCE pearls

BILATERAL ITCHING is the hallmark of allergic conjunctivitis — without itching, look elsewhere.
Topical olopatadine (antihistamine + mast cell stabilizer) is the workhorse — once-daily 0.7% formulation has good efficacy.
AVOID prolonged topical corticosteroids without ophthalmology supervision — cataract, glaucoma, and HSV reactivation risk.
Topical decongestant drops (naphazoline, tetrahydrozoline) cause rebound hyperemia with chronic use — discourage.
VKC and AKC are sight-threatening atopic phenotypes — refer to ophthalmology; treat eye rubbing to prevent keratoconus.
Contact lens wearer with itching + mucus + giant papillae = giant papillary conjunctivitis — change lens type/material or discontinue.

References

AAO 2018 — American Academy of Ophthalmology. Conjunctivitis Preferred Practice Pattern. Ophthalmology 2019;126(1):P94-P169
AAAAI 2020 — Bielory L et al. ICON: Diagnosis and Management of Allergic Conjunctivitis. Ann Allergy Asthma Immunol 2020;124(2):118-134

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