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 μl) containing a known amount of Hm-fluorophore as reference standard is instilled in the conjunctiva fornix. After a few seconds 20 μl of tear fluid is collected: 10 μl are immediately analysed and 10 μl 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 μ 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. Evaluation de l'irritation occulaire due aux cosmetiques par la determination de l'histamine lacrimale Resume De maniere aevaluer l'irritation occulaire provoquee par les produits chimiques et cosmetiques, nous avons voulu presenter dans cet article une methode basee sur l'evaluation de la teneur en histamine (Hm) dans les larmes. L'histamine est mesuree au niveau de picomoles en chromatographie en phase liquide et en detection fluorimetrique apres la derivatisation fluorescamine/histamine. Pour eviter toute irritation ou stimulation incontrolee de la conjonctive pendant la prise de l'echantillon, un procede de lavage de la conjonctive a ete mis au point. En prenant pour base 50 μl d'une solution saline contenant une quantite connue d'histamine fluorophore on instille cette solution dans le cul-de-sac inferieur de la conjonctive. Quelques secondes apres on preleve 20 μl: 10 μl sont analyses immediatement et 10 μl apres la reaction de la derivatisation. De cette maniere il est done possible d'evaluer la dilution lacrimale et de mesurer la teneur en Hm en moins de 10 minutes.