Demodex Testing in Rosacea: Evidence Strength, Clinical Utility, and a Decision-Oriented Approach: A Narrative Review

Demodex mites are found at a higher average density in rosacea than in controls, but this association is often converted too readily into diagnostic and treatment rules.This narrative review uses the hierarchy of diagnostic-test evaluation to appraise five successive claims: association with rosacea, dependence of measured density on the sampling method, validity of a universal threshold, prediction and monitoring of treatment response, and effect on patient outcomes.PubMed and Google Scholar were searched, supplemented by citation chasing, and 39 clinical studies were appraised narratively.Evidentiary strength declined at each step from biology toward clinical action.Association and method dependence were strongly supported.The threshold of more than 5 mites/cm² is an operational convention rather than a universal disease boundary; baseline density does not identify who should or should not receive ivermectin, and falling counts during therapy are not a validated surrogate for clinical benefit.No comparative study has shown that Demodex-test-guided care improves outcomes over phenotype-guided care.Current evidence therefore does not support routine testing in typical rosacea.Testing is justified when a folliculocentric, scaly, asymmetric, corticosteroid-modified, or treatmentrefractory eruption makes demodicosis a genuine differential diagnosis and the result will change management.Dermoscopic Demodex signs can raise pretest probability, and every result should be reported with its method, site, sampled area, number of samples, units, and threshold.