Evaluation of quality and safety parameters of DEET commercial repellents: photostability, penetration/permeation and eye irritation studies

N',N'-diethyl-m-toluamide (DEET) is the repellent most commonly used against mosquito vectors of diseases such as dengue, yellow fever and chikungunya. In Brazil, DEET is marketed in aerosol, solution, lotion and gel forms, at concentrations ranging from 6.65 to 25%. In this study, the kinetic degradation under UVC radiation was studied, as well as the penetration/permeation and the ocular irritant potential of DEET repellents in the form of solution, lotion and gel. The photostability study was conducted over 96h, and the DEET degradation kinetics under UVC radiation was fitted to the zero-order model for the three formulations; t90% values of 23.7 h, 17.0 h and 16.1 h were obtained for gel, lotion and solution forms, respectively. The in vitro skin penetration/permeation using the vertical Franz cell in pig skin showed that all the formulations penetrated/permeated the skin layers, at a higher rate when the lotion (p<0.05) was used, possibly due to its qualitative composition. The in vitro ocular irritant potential using the HET-CAM method indicated that one of the products evaluated was classified as "moderate irritant" and five as "severe irritant”. The set of data indicated the lower penetration/permeation of the solution form and reinforces the importance of being careful during application, to avoid accidental contact with the eyes.