Allergic Conjunctivitis
Conjunctivitis is an inflammation of the conjunctiva, the thin mucous membrane lining the anterior part of the sclera (bulbar conjunctiva) and the undersurface of the eyelids (palpebral conjunctiva). It can be due to allergic or immunological reactions, infection, mechanical irritation, neoplasia, or contact with toxic substances.
This updated UKMLA guide to allergic conjunctivitis is based on NICE CKS, which covers causes, risk factors, symptoms, diagnosis, and management.
Causes and Risk Factors
Allergic conjunctivitis is caused by an IgE response to an allergen (type 1 hypersensitivity)
- Activation of histamine H1 receptors in the conjunctiva leads to ocular itching
Allergic conjunctivitis often co-exists with other atopic conditions, the atopic triad:
- Atopic dermatitis (eczema)
- Asthma
- Allergic rhinitis
Allergic conjunctivitis is most commonly seasonal or perennial, but more severe forms such as vernal keratoconjunctivitis and atopic keratoconjunctivitis can involve the cornea and may require ophthalmology input.
Clinical Features
Most cases of allergic conjunctivitis are seasonal and typically occur in spring and summer
Hallmark: bilateral ocular itching (may also be described as a burning or stinging sensation)
Other clinical features (also bilateral, typically):
- Watery or mucoid discharge
- Hyperaemia injection (conjunctival redness)
- Chemosis (conjunctival swelling)
- Eyelid oedema
Investigation and Diagnosis
First, exclude red flags of a red eye warranting referral. See the Red Eye Referral article.
Allergic conjunctivitis is primarily a clinical diagnosis, investigations are not normally required.
Management
General / Conservative Management
Advise the patient on:
- Allergen avoidance
- Avoid rubbing the eyes
Symptomatic management measures:
- Cold compresses to the eyes
- Application of ocular surface lubricants (e.g. artificial tears and saline solution)
Pharmacological Management
If non-pharmacological measures do NOT provide adequate relief, consider:
- Topical antihistamine (e.g. antazoline – contains antihistamine + xylometazoline), OR
- Dual action mast cell stabiliser / topical antihistamine (e.g. azelastine, epinastine, ketotifen, olopatadine)
- Examples of mast cell stabilisers: sodium cromoglicate, lodoxamide
If ineffective despite 1st line therapy: consider adding topical ocular diclofenac
Antazoline and other products that contain a vasoconstrictor agent should NOT be used for more than 7 days, as chronic use is associated with rebound vasodilation upon withdrawal (similar to intranasal decongestants).