Diagnosing allergic conjunctivitis is usually easy for the GP or the pediatrician. The help of the ophthalmologist is needed in severe cases to exclude implication of the corneal membrane. Concerning adults the condition can be misdiagnosed by the occurrence of dry eye syndrome. Other conditions such as ocular rosacea, blepharitis can also mimic some signs of allergic conjunctivitis.

The allergist should be required in cases of seasonal and acute allergic conjunctivitis (SAC), especially if occurring circumstances are always similar (for instance in a particular place or in a precise season or after contact with any pet). In these cases immediate reactions to allergens are implicated. They are investigated through prick-tests and serum specific IgE dosages. In addition a conjunctival provocation test can be performed. In seasonal cases pollens are frequently involved, as well as moulds. Pet dander and mites are more frequent in recurrent SAC. PAC is a very good indication of allergic investigation, even if non specific triggers are suspected. House dust mites and other perennial allergens could be involved. VKC and AKC require specialized investigations targeted towards allergens responsible for immediate and non immediate hypersensitivity reactions. Regarding that non immediate reactions, drugs and additives could be investigated on through patch-tests. As far as GPC is concerned it requires no allergic investigation but at least avoidance of soft lenses. It is appropriate to remember that in all of these cases, allergic triggers can be associated to various co morbidity factors such as dry eye, refraction troubles, and psychological factors.