How long does neem oil remain effective after application?
Written by
Paul Reynolds
Reviewed by
Prof. Charles Hartman, Ph.D.The effectiveness of neem oil can vary depending on how it is applied and environmental factors. For example, neem oil applications made outside last 7-10 days barring rainfall, and neem oil surfaces made with indoor disinfectant are effective for 72 hours. Once properly stored in amber glass and kept at a temperature below 77 degrees Fahrenheit (25 degrees Celsius), skincare blends will last six months; therefore, an example will be given involving one of my clients rose bushes during which rose bushes were brought back to health in six months.
Garden Applications
- Reapply after heavy rain or irrigation
- Morning sprays reduce UV degradation risks
- Add 1 tsp castile soap per liter to improve rainfastness
Skincare Storage
- Use amber glass bottles to block light degradation
- Avoid temperatures above 25°C (77°F)
- Discard if rancid odor develops
UV degradation greatly reduces neem oil's efficacy over time outdoors. If you live in an area that rains often, you may need to reapply every 5 days instead of 10. My friend learned about the reduced efficacy of neem oil after dealing with returning aphids in the middle of the week. By applying neem oil in the evening, he was able to apply the treatment 3 additional days!
For the control of pests indoors, the residual effects of neem dissipate quickly from air movement and cleaning. Before reapplying, wipe off the treated area to avoid excessive oil collection. I save frequent use for high-traffic areas every week and hidden areas on a biweekly schedule.
Read the full article: 10 Versatile Neem Oil Uses for Home & Health
