Stabilizing effect of epsilon-aminocaproic acid on allergenic extracts.

The effect of epsilon-aminocaproic acid (EACA) on the degradation of an aqueous Lolium perenne extract was studied by intracutaneous tests and by RAST inhibition. Extracts for skin testing stored at 4 degrees C for 12 months and at 37 degrees C for 6 weeks were significantly protected from degradation by addition of 0.1 mol/L of EACA before storage. Extracts were stored for RAST inhibition at 4 degrees C for 6 months and at 37 degrees C for 7 days. Shelf life was twofold to threefold increased when 0.1 mol/L of EACA was added to the dilution medium. EACA also protected the extracts from the effect of freezing and thawing. Comparison with the effect of human serum albumin indicated a rather short activity of human serum albumin, whereas the effect of EACA lasted longer. It is suggested that EACA can be used to increase the stability of aqueous allergen extracts for skin testing and for hyposensitization therapy.