Abstract: A method of characterizing specific microbiota associated with Demodex mites from a rosacea patient is described. The method can include a step of realizing a biopsy on the patient and analyzing the microbiota based on a method of 16SrRNA sequencing or pyrosequencing. A method for the diagnosis of rosacea in a patient is also described. This method can include characterizing microbiota associated with Demodex mites in the patient. Also described, are methods of differentiating a subtype of rosacea in a patient with rosacea and methods of controlling and measuring an active agent's treatment effectiveness on rosacea.