Study summary
Harnessing insect-derived oils for enhanced efficacy of plant-based repellents against disease-transmitting mosquitoes
Ochola JB, Mudalungu CM, Mokaya HO, Cheseto X, Onsomu GN, Sevgan S, Kelemu S, Torto B, Tanga CM, et al.
Read the original paper- Study type
- Lab
- Year
- 2026
- Sample size
- 8 subjects
- Species tested
- Anopheles gambiae; Aedes aegypti; Culex quinquefasciatus
- Published in
- Scientific Reports 16:7662 (2026), DOI 10.1038/s41598-026-38831-x
- Evidence strength
- Limited evidence
How it was tested
Arm-in-cage complete-protection-time tests with eight volunteers, comparing plant essential oils alone against 1:1 blends with edible-insect oils (locust, cricket, termite) as fixatives, versus a 20% DEET control, with skin volatiles profiled by GC-MS.
What it measured
Measured complete protection time, by arm
Positive control in this study (3.75 h).
Best blend; insect-oil fixative roughly doubled citronella's protection, comparable to 20% DEET (225 min) over the first 3.5 h.
Best blend (2.81 h).
Best blend (2.56 h).
Essential oil alone (~40% in ethanol carrier); about 1.8 hours.
Complete protection time = minutes until the first confirmed bite.
Summary
Laboratory arm-in-cage study testing whether oils rendered from edible insects (desert locust, nsenene cricket, and termite) can work as fixatives that slow the evaporation of plant essential oils and so extend their repellency. Three plant oils (citronella, African camphor basil, and lemon eucalyptus) were blended with the insect oils and applied to the forearms of eight volunteers, with complete protection time measured against three mosquito species and skin volatiles tracked by GC-MS.
Key findings
Citronella essential oil on its own gave about 1.8 hours of complete protection, but a 1:1 blend of citronella with termite (Macrotermes) oil roughly doubled that, reaching a median complete protection time of 3.50 hours against Anopheles gambiae, 2.81 hours against Culex quinquefasciatus, and 2.56 hours against Aedes aegypti. That best blend held repellency comparable to the 20% DEET positive control (3.75 hours) over the first 3.5 hours, staying at 100% protection at 180 minutes and 93.4% at 270 minutes against An. gambiae. GC-MS showed the insect oils act as fixatives, forming esters (geranyl acetate, geranyl propanoate, citronellyl acetate) that kept the active plant volatiles on the skin for over 180 minutes. This is direct evidence that citronella's short protection window is largely an evaporation problem that formulation can address.
Limitations
Small laboratory study of eight volunteers using caged, colony-reared mosquitoes rather than a field trial, so real-world durability is unconfirmed. The fixatives are insect-derived oils that are not commercial repellent ingredients and are not sold in consumer products, so the practical takeaway is about formulation science and citronella's potential rather than a product a shopper can buy today. Even the best blend fell short of DEET after the first 3.5 hours, and reported protection times carry meaningful variability (standard deviations of roughly half an hour).