الفهرس 
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Abstract
General Principle of Allergic Conjunctivitis
Allergy or hypersensitivity is an abnormal reaction of the tissue to forign substance (allergens).
The conjunctiva is a frequent site of allergic reactions, it is readily accessible to air borne or contact allergans and is frequently exposed to drugs and owing to its proximity of the delicate skin of the lids often results in combined allergic dermatoconjunctivitis.
(Duke Elde 1977)
According to (Boyed and Aaron 1972), the allergy occurs as an antigen—antibody reaction at the second exposure or after a week from the first exposure at the same or other sites, and it is less dependent on the amount of forign substance, duration of application and site of contact.
On the other hand hypersensitivity is more intense reaction than normal at the site of contact as a result of local irritation, the reaction occurs on the first exposure at the site of contact and its intensity depends on the amount of forign substance, duration and site of contact.(Sorsby A. 1972)
The work of Sherman and Itidman (1950) by comparative effects of intramucosal and intracutaneous injections, has shown that the conjunctiva is 10 times more sensitive than skin.
An allergen is an antigen which gives rise to allergic symptoms in a susceptible person, most are proteins and a few are polysaceharides, some simple chemicals,a few inorganic substance become allergenic by combination with protein inside the body to form compounds with which anaphylac tic intoxication can be produced. These compounds are known as (Hapten).
(Landsteiner 1924)
The work D’Ermo (1953) points to the probability that atropine for example, form stable salts with some of the proteins in the tear and when atropine sulphate is allawed to stand in lacrimal fluid for a large time to permit chemical redistribution between the sulphate and acid protein radicals, the resultant solution on subconjunctival injection produces a typical skin test in many sensitive persons with some occular symptoms.