Does Castor Oil Kill Demodex Mites? What a 2025 University of Auckland Study Found

Castor oil is widely recommended for eyelid health, but until recently there was little direct evidence about whether it actually affects Demodex mites. A 2025 study from the University of Auckland set out to test exactly that — in a controlled laboratory setting. Here's what it found, in plain terms.

How the study worked

Researchers at the Aotearoa New Zealand National Eye Centre collected live, moving Demodex mites from epilated eyelashes that showed cylindrical dandruff. They then exposed the mites to small (5 µL) amounts of different oils and watched under high magnification — checking for movement every five minutes for up to 480 minutes (eight hours) — recording survival time as the point when the mite stopped moving. This is called an ex vivo study: done on mites removed from the lash, in the lab, rather than on people's eyes.

What they tested

• 100% cold-pressed castor oil

• A proprietary castor oil preparation combined with manuka and kanuka oils

• 100% and 50% tea tree oil (as positive "known-effective" controls)

• Unexposed mites (negative control)

The results

The headline: both castor oil preparations shortened Demodex survival compared with unexposed mites, confirming genuine anti-Demodex activity. Tea tree oil worked much faster (minutes rather than hours), which is expected — but tea tree is also far more irritating to the delicate eye area.

So, does castor oil "kill" Demodex?

In the lab, yes — castor oil reduced mite survival, with mites ceasing movement within roughly four to five-and-a-half hours. It's slower than tea tree oil, but crucially it's gentle and well tolerated, which matters for something you'd use around your eyes regularly. The authors noted that bringing survival under the eight-hour mark supports overnight castor oil application as a practical way to act on the mites while you sleep.

An honest caveat

This was an ex vivo laboratory study on mites removed from lashes, not a clinical trial on patients — so it demonstrates biological plausibility and rationale, not a proven cure. The researchers concluded the findings justify further clinical testing. Still, combined with an earlier trial showing castor oil reduced cylindrical dandruff on real eyelids, the case for gentle castor oil against Demodex is genuinely encouraging.

Try the gentle route: Meibocare LidBoost+ is 100% cold-pressed castor oil — the same category of oil used in this research — with a roller-ball applicator ideal for overnight lash-line use.

Frequently asked questions

Does castor oil kill Demodex mites?

In a 2025 ex vivo (laboratory) study, castor oil shortened Demodex mite survival to roughly four hours, confirming anti-Demodex activity. It's gentler but slower-acting than tea tree oil, and clinical trials are still needed.

Is castor oil or tea tree oil better for Demodex?

Tea tree oil kills mites faster in the lab but can irritate the eye area; castor oil is slower but gentle enough for regular overnight use. Many people tolerate castor oil better long-term.

Educational information only, not medical advice. Reference: Jennings CJ, Craig JP, et al. Anti-Demodex activity of castor oil confirmed in an ex vivo study. Contact Lens and Anterior Eye. 2025. doi:10.1016/j.clae.2025.102471 (PubMed)