Study summary
Comparative efficacy of insect repellents against mosquito bites (complete-protection-time study)
Fradin MS, Day JF
Read the original paper- Study type
- Lab
- Year
- 2002
- Sample size
- 15 subjects
- Species tested
- Aedes aegypti
- Published in
- New England Journal of Medicine 347(1):13-18
- Evidence strength
- Definitive evidence
How it was tested
Arm-in-cage complete-protection-time (CPT) tests: 15 volunteers inserted a treated arm into a cage of unfed Aedes aegypti at intervals until the first confirmed bite.
What it measured
Measured complete protection time, by arm
Wearable format — essentially no protection.
Complete protection time = minutes until the first confirmed bite.
Summary
The landmark complete-protection-time study: Fradin and Day timed how long 16 store-bought repellents kept Aedes aegypti from biting, in controlled arm-in-cage tests with 15 volunteers. It is the study that put hard numbers on the idea that DEET lasts and botanicals do not.
Key findings
Protection tracked DEET and its concentration above all else. A 23.8% DEET spray lasted about 5 hours (301 minutes), 20% controlled-release DEET about 4 hours, and lower-concentration DEET proportionally less. The only non-DEET product that came close was a 2% soybean-oil repellent at about 95 minutes; every citronella product lasted roughly 10 to 20 minutes, IR3535 about 23 minutes, and all three repellent wristbands gave essentially zero protection. Each step up in DEET concentration bought significantly more time.
Limitations
One mosquito species in one indoor lab, so it misses wind, sweat, and field biting pressure; the fixed-interval testing can slightly overestimate short-acting products; and the study had industry funding, though the authors report the analysis was done independently.