What is allergic conjunctivitis?
Allergic conjunctivitis is characterised by an allergic inflammation on the eye surface. It may manifest alone or accompanied by other allergic diseases, such as allergic rhinitis.
Is allergic conjunctivitis common?
Allergic disorders of the eye are very common. Seasonal conjunctivitis is the most common form and is generally associated to rhinitis in 65% of cases.
In the perennial form, the symptoms manifest year-round.
What are the causes of allergic conjunctivitis?
Seasonal allergic conjunctivitis involves the same airborne-allergens that cause allergic rhinitis: tree, grass and weed pollen.
In those who suffer from perennial conjunctivitis, the allergens tend to be house dust mites, desquamation of epithelial cells in pets, mildew spores, cockroaches, latex particles and some food allergens.
In contact allergic conjunctivitis, allergens to plants, medicines, cosmetics, latex and ophthalmic preservatives (benzalkonium chloride and thiomersal) are more important.
Why does allergic conjunctivitis occur?
It occurs due to an exaggerated reaction of the tissue which is most immunologically active, the conjunctiva (the white part of the eye).
Airborne or contact allergens are solubilised in the tear film, they cross the conjunctiva and are processed, binding to IgE receptors present in cells called local mast cells, generating inflammation as they degranulate (allergic response).
How does allergic conjunctivitis manifest?
Allergic conjunctivitis can be seasonal (during one time of year) or perennial (year-round), atopic keratoconjunctivitis (associated to atopic dermatitis), contact or vernal (chronic variety associated to states of atopia or allergy).
What are the symptoms of allergic conjunctivitis?
Seasonal conjunctivitis is characterised by itching and a sensation of burning or sharp pain, watery eyes or reddening of the conjunctiva. The symptoms progress with exacerbations and remissions during the entire allergy season.
The perennial form is expressed by classic signs such as congestion of the blood vessels and oedema of the conjunctiva and eyelids.
How is it diagnosed?
Diagnosis is performed by an allergy specialist and/or ophthalmologist using medical history, symptoms, physical examination, skin tests and blood analyses.
How is it treated?
Allergic conjunctivitis is treated using:
- Environmental or preventive control, use of sunglasses and other measures to avoid airborne or contact allergens.
- Medications: anti-inflammatory eye drops, antihistamines in tablets.
- Vaccines or specific immunotherapy, always controlled and followed-up by an allergy specialist.