Histamine determination in tears as an index of safety in use of cosmetic products.

Synopsis To assess ocular irritancy caused by chemical and cosmetic products a reliable method based on evaluation of histamine (Hm) in tears is presented. Hm is measured at picomole levels by HPLC and fluorimetric detection after fluorescamine-HM derivatization. In order to avoid any uncontrolled irritation and stimulation of the conjunctiva during sample collection, a procedure of conjunctiva lavage was developed. A balanced salt solution (50 mul) containing a known amount of Hm-fluorophore as reference standard is instilled in the conjunctiva fornix. After a few seconds 20 mul of tear fluid is collected: 10 mul are immediately analysed and 10 mul after derivatization reaction. In this way it is possible to evaluate tear dilution and to assess Hm content in less than 10 minutes. In a group of 20 normal subjects Hm has been determined in comparison with that of two volunteers after topical application of 50 mu of 0.2% and 0.4% sodium lauryl sulphate solution. A contact of 30 seconds of the cosmetic ingredient caused an immediate dose-dependent Hm release through a direct cytotoxic damage of cell membranes due to the surfactant action.