AKT · Ophthalmology/Lids & surface

Allergic conjunctivitis

Type I hypersensitivity of the conjunctiva (seasonal/perennial; vernal/atopic in severe forms)

Overview

IgE-mediated conjunctival hypersensitivity. Bilateral itch (the cardinal symptom) with watering, chemosis and stringy mucus, on an atopic background. Treated with allergen avoidance, antihistamine/mast-cell-stabiliser drops. Vernal and atopic keratoconjunctivitis are severe, sight-threatening variants.

Recognise

Bilateral ITCHING (the hallmark), watering, redness and lid swelling
Chemosis (conjunctival oedema) and stringy/ropy mucoid discharge; cobblestone tarsal papillae in chronic/vernal disease
Personal/family atopy (hay fever, asthma, eczema); seasonal or perennial pattern

Red flags

Vernal/atopic keratoconjunctivitis with shield ulcer, photophobia and reduced vision → ophthalmology (sight-threatening)

Differentials & how to tell them apart

Viral conjunctivitiswatery + preauricular node + URTI, but NOT itch-dominant

Bacterial conjunctivitispurulent discharge, no itch

Dry eye / blepharitisgritty burning rather than itch; lid-margin signs

Allergic conjunctivitis — chemosis and conjunctival injection
James Heilman, MD / CC BY-SA 4.0 — Wikimedia Commons

Investigations

Clinical. No routine tests.

Management

Allergen avoidance + topical antihistamine / mast-cell stabiliser

1Avoid allergens, cool compresses, lubricants and avoid eye-rubbing. Add a topical antihistamine or dual-action mast-cell stabiliser; mast-cell stabilisers need ~2 weeks to work so are for recurrent/persistent disease.Gate: Severe vernal/atopic disease with corneal (shield) ulcer or visual loss → refer; reserve topical steroids for specialist supervision (glaucoma/cataract/HSV risk)
2Inadequate control → add oral antihistamine, topical NSAID, or specialist-supervised topical steroid; refer vernal/atopic keratoconjunctivitis.

Allergen avoidance + cool compresses + lubricants — first-line non-pharmacological

Topical antihistamine / dual-action mast-cell stabiliser — e.g. olopatadine; sodium cromoglicate needs ~2 weeks loading for prophylaxis

Oral antihistamine — for associated rhinitis/systemic symptoms

Topical ocular diclofenac / short steroid course — adjunct/severe — steroids only under specialist guidance

Key points

Itch = allergy until proven otherwise. Stringy mucus and chemosis with bilateral symptoms and atopy clinch it.

Monitor & prognosis

Symptom control through the season.

Good; vernal disease often improves after puberty.

Source: NICE CKS Conjunctivitis – allergic