Northern California mosquito field tests support complete protection times of 12 hours for an IR3535 lotion and 11 hours for a wipe formulation, according to EPA science reviewers. The study addressed a weakness in earlier Florida research: too few mosquitoes landing on untreated volunteers at one site to support a longer protection-time finding.
The findings concern research conducted in November 2023, not a newly approved label. EPA has posted both scientific and ethics reviews among its Human Studies Review Board materials. Together, they examine whether the results are scientifically usable and whether researchers adequately protected the people who volunteered for mosquito exposure.
LivFul Inc. sponsored the study, and Carroll-Loye Biological Research conducted the fieldwork on November 19 and 20, 2023. Both formulations contained 20% IR3535. The study report was completed June 17, 2025, and an addendum followed January 13, 2026.
The central question was how long the products prevented a confirmed mosquito landing on treated skin. Researchers used that first confirmed landing as the study endpoint. EPA’s science review, by biologist Shweta Sharma and senior entomologist Kevin Ulrich, concluded that the California data supported 12 hours for Akiva 20 lotion and 11 hours for Akiva 20 Wipe.
Why mosquito landing pressure matters
Measuring repellent performance requires mosquitoes to be active enough to challenge the products. EPA’s testing guideline calls for untreated control subjects to experience at least one mosquito landing per minute before testing begins and intermittently throughout testing. For a five-minute exposure period, the expected minimum is approximately five landings.
That requirement shaped EPA’s interpretation of the earlier Florida study. At Site 1, adequate mosquito landing pressure on untreated controls persisted for more than 12 hours. That describes the strength and duration of the test conditions, not a finding that both products provided more than 12 hours of complete protection.
At Florida Site 2, low landing pressure limited the supported complete protection time to 3.5 hours. Considering both sites, EPA conservatively estimated three hours for both products. The agency’s policy uses the more conservative site result, rounded down to a whole hour, when selecting a protection time for labeling.
The California study was intended to replace the weak Site 2 data, rather than repeat the entire Florida study. EPA reviewers found that the California site achieved adequate landing pressure and supported the longer protection times. The distinction matters: few mosquito landings can reflect weak test conditions rather than sustained repellent performance.
Field conditions and pathogen surveillance
The fieldwork took place in Butte and Glenn counties, in a region with rice acreage and riparian habitat. EPA’s review describes flooded rice cultivation and flooded wildlife refuges as supporting mosquito breeding and larval development. That agricultural landscape provided the setting for the research, which tested repellents on human skin rather than crop pest-control products.
Researchers also monitored the area for mosquito-borne pathogens. For a month before testing, they checked three subsites weekly using six mosquito traps. The study director reviewed state health reports and coordinated with local mosquito control districts. EPA’s review reports no detected vector-borne disease within 25 miles of the proposed site during the preceding four weeks.
Mosquito samples went to the University of California, Davis arbovirus laboratory for screening. Aedes and Culex samples were tested for West Nile, St. Louis encephalitis and Western equine encephalomyelitis viruses. Aedes mosquitoes also underwent testing for Zika, dengue and chikungunya. None of those screens detected pathogens.
The science review identified a laboratory-practice exception: testing used to generate the products’ certificate of analysis did not follow Good Laboratory Practice standards, and specific reasons were not provided. Nevertheless, EPA reviewers concluded that the report contained enough information to make an informed judgment about study integrity.
Human-subject safeguards and agency review
EPA’s ethics review explains that human volunteers were used because reliable substitutes have not been found to adequately predict how long skin-applied repellents work. Institutional review boards reviewed the protocol and participant materials. After the work transferred from Louisiana State University to Carroll-Loye in August 2023, oversight moved to WCG’s institutional review board.
According to the ethics review, 82 people completed informed consent, which is not a count of field-test participants. Staff explained the study, risks, eligibility requirements and procedures, emphasized that participation was voluntary, and checked understanding. Pregnant and nursing women could not enroll.
EPA ethics officer Michelle Arling concluded that the research met applicable human-subject protection standards and documentation requirements. Her conclusion about EPA relying on the study was conditional: the research must also be scientifically acceptable. The ethics memorandum states that relying on scientifically invalid research would not be ethical.
EPA must seek Human Studies Review Board input before relying on covered intentional-exposure research. Under its charter, the board advises EPA on scientific and ethical questions; it does not make the agency’s regulatory decisions. The protection times remain findings attributed to EPA’s science reviewers, distinct from an approved label claim or a final board determination.
