 Qytosan is a popular polysaccharide used in the development of drug delivery systems due to its unique physical and chemical characteristics. It can be used to form nanoparticles and microparticles and has been shown to have high nucoadhesive properties. Despite its potential applications, there is limited research into the biocompatibility of Qytosan carriers. This review discusses the current state of knowledge regarding the biocompatibility of Qytosan carriers, focusing on the use of in vitro and in vivo models. The authors also highlight the limitations of existing studies and suggest areas where more research is needed. This article was authored by Ana Grenja, Susana Rodriguez, Carmen Ramunan Lopez and others.