Sodium Cromoglycate 2% sterile Eye Drops inhibits the release of chemical mediators from sensitised mast cells and is capable of rapid phosphorylation of mast cell protein. The exact mechanism of action of the drug remains to be elucidated but Sodium Cromoglycate appears to modulate the allergic response to antigen antibody interactions in a way which prevents the subsequent formation or release of toxic or inflammatory mediators. Sodium Cromoglycate 2% Eye Drops appears to act mainly through a local effect on the mucous of the eye. Approximately 0.03% of an ophthalmic dose of Sodium Cromoglycate 2% Eye Drops is absorbed systemically. Sodium Cromoglycate 2% Eye Drops prevent, release of mediators of type-I allergic reactions, including histamine and slow reacting substance of anaphylaxis (SRS-A) from sensitised mast cells after the antigen antibody union has taken place. The drug does not inhibit the binding of IgE to mast cells nor the interaction between cell bound IgE and the specific antigen; instead Sodium Cromoglycate suppresses the release of substances (e.g. histamine, SRS-A) in response to this reaction. The drug also inhibits Type-III (late allergic, Arthus) reactions.