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ASTM E939
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Quick understanding of the test
ASTM E939 - Standard Test Method of Field Testing Topical Applications of Compounds as Repellents for Medically Important and Pest Arthropods (Including Insects, Ticks, and Mites),Mosquitoes
ASTM E939 evaluates the repellency of compounds that have undergone primary laboratory testing and are approved for skin application for secondary testing.
Application
Applicable to topical insect repellents designed for use against mosquitoes and other medically significant arthropods.
- Test-repellent solutions are applied to limbs and exposed to natural mosquito populations in the test area, and the time to the first confirmed bite (CPT) is recorded.
- Data is analyzed to evaluate repellent efficacy and compare performance with a standard control.
- This test method ensures the effectiveness and reliability of mosquito repellents during the final phase of development for personal use.
- Simulates real-world conditions to test repellents effectively.
Turnaround Time
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Abstract
ASTM E939 standard test method assesses the efficacy of repellents designed for the protection of people against medically important arthropods, such as mosquitoes and ticks. This test method involves volunteers who meet all the criteria for this test. A measured amount of the repellent is applied to the subject’s skin, and this most often is the forearm or lower leg; then the treated area is exposed to the mosquitoes in the field setting. The primary objective of this test method is to determine how long the repellent gives protection against mosquito bites.
ASTM E939 Test Methodology
The test methodology for this standard is as follows:
Pre-test preparation
- Mosquito species present at the site are confirmed and their peak activity period is determined. Test start and stop times are set accordingly.
Limb surface areas of subjects are measured so that application rates remain uniform across individuals.
Product application
- Candidate repellents are initially tested at 25% concentration in ethanol, with 25% DEET included as a reference standard.
- A volume of 1.0 mL is applied evenly to the forearm (or 1.5 mL to the lower leg if leg exposure is appropriate for the target species). Application is carried out in paired comparisons at equal concentrations on opposite limbs.
Experimental Design:
- Paired Tests: When testing one or two repellents, direct paired comparisons with DEET are used.
- Balanced Incomplete Block (BIB) Design: When multiple repellents are tested, subjects rotate treatments to reduce bias from individual attractiveness to mosquitoes.
Field Testing
A treated limb is exposed to natural populations of mosquitoes from the test area. Intermittent movement (walking, squatting, raising arms) may be included to attract mosquitoes, depending on species behavior.
Observation & Data Recording:
- Mosquito landings and bites are recorded. Mosquitoes are collected in vials for species identification when needed.
- A Complete Protection Time (CPT) is defined as the interval from application until the first confirmed bite (a second bite within 30 minutes confirms failure of protection).
- Ratios of candidate repellent effectiveness to DEET are calculated for reliability across different conditions.
Importance of ASTM E939 Test
ASTM E939 provides a standardized, real-world field test that proves how long and how well a product protects against mosquitoes compared to the DEET benchmark. This not only helps meet regulatory requirements but also guides product development, supports strong marketing claims, and builds consumer trust by showing the repellentโs performance under natural biting conditions.
Strengths of ASTM E939 Test Standard
1. Real-World Relevance
- Conducted under natural field conditions, directly exposing treated skin to wild mosquito populations.
- Captures real biting behavior, environmental variability, and species diversity that lab tests cannot fully replicate.
2. Standardized & Comparable
- Uses DEET (25% in ethanol) as the reference standard, allowing direct comparisons across different compounds and studies.
- Clear definition of Complete Protection Time (CPT) provides a consistent, measurable endpoint.
3. Flexibility
- Can be adapted to different mosquito species (diurnal/nocturnal) and geographical locations.
- Applicable to a wide range of repellent formulations (solutions, lotions, creams, aerosols).
4. Robust Experimental Design
- Balanced Incomplete Block (BIB) design accounts for differences in individual human attractiveness to mosquitoes.
- Paired-arm testing reduces variability since the same subject simultaneously tests two repellents.
5. Comprehensive Data Collection
- Measures protection time.
- Biting pressure (untreated control exposure).
- Species-specific efficacy (via mosquito identification).
- Product attributes (odor, staining, oiliness, etc.).
Conclusion
At Microbe Investigations Switzerland, we provide expert field testing services following the ASTM E939 standard to evaluate the effectiveness of topical repellents. With our precise methodologies and real-world testing environments, we help ensure your products deliver dependable protection and meet the highest industry benchmarks.
Ready to validate your repellentโs performance? Reach out to our team today to discuss how we can support your testing needs!
Frequently Asked Questions
DR. Martinoz Scholtz
ASTM E939 is a standardized field test that measures how long topical repellents protect against mosquito and other arthropod bites under natural conditions. It provides real-world data on product effectiveness.
ASTM E939 test is applicable to topical repellents such as lotions, creams, gels, sprays, and active ingredients designed to protect against mosquitoes, ticks, mites, and other biting arthropods.
Turnaround time typically ranges from a few days to several weeks, depending on product type, number of samples, and field conditions.
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