Allergic eye disease is a common ocular problem. It is one part of the whole spectrum of allergic diseases which share a common initiating mechanism and a characteristic pattern of inflammation.

The association between exposure to airborne plant pollens and the development of ocular and nasal symptoms in itself was noted by Charles Blackley in 1873.1 The classification of allergic eye diseases is based entirely on clinical features, which in the past has resulted in the use of inappropriate or unsatisfactory treatments, owing to our lack of knowledge of the underlying mechanisms. Recent work has defined such underlying pathogenic mechanisms of allergic eye disease, extending our knowledge of the cellular and mediator mechanisms involved, and enabling pathophysiological correlates to be made between the clinical patterns of disease and responses to treatment. This is now resulting in a clearer understanding of the disease processes which, in the long term, holds promise for the development of more effective treatments.

As the prevalence of allergic disease is increasing, probably through environmental factors, it is appropriate at this stage to review our current knowledge of the mechanisms of allergic eye disease.

The morbidity and mortality of asthma have increased in the past few years2-5 with no corresponding rise in the underlying rate of atopy itself.6 Environmental causes have been cited as responsible for this, as the rising trends have occurred too quickly for genetic causes to have exerted their effects.6The increase in asthma has coincided with an increase in house dust mite levels, and is greatest in communities exposed to high allergen levels.2 However, there are no firm data available on which to base any change in the incidence of allergic eye disease.

The reported incidence rates for the different forms of allergic eye disease have been varied. …