Conjunctivitis is usually allergic or infective. Four common types of allergic conjunctivitis are seen as follows: seasonal, perennial, giant papillary, and contact dermatoconjunctivitis.
This article will cover seasonal allergic conjunctivitis (SAC), which is caused by exposure to allergens such as grass pollen, tree pollen, mould spores or weeds in an individual who has been previously sensitised (a pure type 1 hypersensitivity reaction).
In a type 1 hypersensitivity reaction, the body releases IgE antibodies which give rise to the classical symptoms that are observed in patients.1
Those patients with a family history of atopy are seen to be at higher risk of suffering from SAC. It is therefore important to consider this when taking a history from a patient.
‘Hay fever’ is a common condition in the UK with about 1 in 5 people thought to suffer from it, 20% of whom experience eye symptoms (SAC).3 Of all the eye complaints presenting to general practice, it is thought that about 15% are due to allergic conjunctivitis.2 Half of all those patients who present for treatment of allergies have ocular symptoms.3
Allergy seasons in the UK
SAC tends to affect patients in the summer months of May to August when the grass pollen is at its highest levels. However, the tree pollen season can run from as early as February until June and those allergic to weed pollens will be affected from June until September. Therefore, the patient who is allergic to tree, grass and weed pollens may suffer a very prolonged 'hay fever' season, from February to October. Mould spores can be present at any time of the year, but are particularly prominent during the autumn and in mild damp conditions (peak time September and October).1
If symptoms are present all year round, then this is usually from indoor allergens such as house dust mite, pets and indoor moulds.
Signs and symptoms of SAC
Good history and examination aid effective diagnosis. Allergic cases typically present bilaterally with red, intensely itchy eyes and watery discharge. Some patients will describe a mild photophobia alongside these symptoms. On examination the following may be seen:
- bilateral red eyes with a clear watery mucoid discharge