Invited review: Evaluation of teat disinfectant efficacy studies from 2014 to 2026-A systematic review

The objective was to systematically review the scientific rigor and findings of peer-reviewed studies published from January 2014 to January 2026 on the efficacy of teat disinfectants used in dairy routines. Following the methods outlined in the Cochrane Handbook for Systematic Reviews, a comprehensive search of PubMed, CAB Abstracts, and BIOSIS Previews was conducted using the terms "dairy" and "teat disinfectant" or "teat dip" within the title or abstract. Articles not written in English or that applied only in vitro methodologies were excluded. Eligible studies were screened for relevance and assessed by 2 reviewers for bias using a scoring rubric derived from evidence-based veterinary medicine checklists (e.g., Consolidated Standards of Reporting Trials; Strengthening the Reporting of Observational Studies in Epidemiology; Systematic Review Centre for Laboratory Animal Experimentation) and published guidelines. Forty-one articles met inclusion criteria, with 21 countries and 28 journals represented. Each was scored across 6 domains: identification and scope, design and execution, outcome reporting, relevance and generalizability, risk of bias and conflict of interest, and overall appraisal. Only 7 studies (17%) demonstrated high scientific merit. Of these, 6 evaluated efficacy based on udder health outcomes (e.g., new clinical or subclinical infections), and one assessed bacterial reduction on teat skin. Postmilking disinfectants were represented in 4 studies, premilking disinfectants in 2, and the last evaluated a product used for both. Germicide selection varied widely and only 2 studies evaluated similar chemicals and controls; both compared chlorine dioxide with iodine but used different application methods (brush vs. dip cup) and timings (pre- vs. postmilking). Most high-merit studies reported noninferiority between products, with odds or risk for new infections ranging from 4.0 to 7.4 per 100 quarters across treatment and control groups for each 1- or 2-wk period at risk. Only one showed a significant advantage for the experimental product. Numerical favorability for the experimental disinfectant was reported in 4 additional high-merit studies, including one with week-dependent differences, and one study favored the control product. The bacterial reduction study showed significant decreases in log of colony-forming units across pathogen groups, though results varied by farm and product concentration. Teat health outcomes (e.g., hyperkeratosis, skin condition) were often included but inconsistently reported. Overall, substantial variability in design and reporting quality was observed, with many studies lacking methodological rigor and applicability. Future research should prioritize guideline-based reporting, appropriate statistical methods, and transparency in funding and limitations to strengthen the evidence base for disinfectant efficacy. Given historical improvements in farm management and changes in pathogen pressures, additional consideration should be made for conducting negatively controlled, randomized clinical trials for teat disinfectants. A need remains for recent, reliable information to support consultants and farm managers in dairy practice.