Objective: The purpose of this study was to compare the acaricidal effect of 5% tea tree oil gel and 2% arilin eye drops on the ocular Demodex folliculorum. Method: Eyelash samples were epilated from out-patient of ophthalmology to collect ocular D. folliculorum

transferred into 6-well plates and examined under the inverted microscope. Each well contained at least 20 live mites which were collected and treated with 5% tea tree oil gel and 2% arilin eye drops

respectively

with normal saline as blank control. Result: 5% tea tree oil gel was demonstrated to show better killing effect on the mite in vitro. After drug treatment

the morphology and activity of D. folliculorum altered with typical changes of excitation-spasm-chalasia-death. In the treatment of 5% tea tree oil gel

the average survival time of mites was (1.43±0.62)h

while in 2% arilin eye treatment

it was (27.65±5.14) h

with a significant difference between them(P<0.01).The survial times of mites

showed significant difference among the three groups(P<0.01). The survival time of D. folliculorum in normal saline group was (23.33±3.98) h

which had significant difference from the 5% tea tree oil gel group(P<0.01);while in the 2% arilin eye drops group the survival time was (27.65±5.14) h

compared with the survival time of control group

there was no significant difference between them. The mortality of mites within 24 hours in 5% tea tree oil gel

2% arilin eye drops and control group were 100%

20% and 50% respectively

and there was a significant difference between them(P<0.01). Conclusion: 2% arilin eye drops has no effect on killing D. folliculorum in vitro

while 5% tea tree oil gel has the killing effect on D. folliculorum in vitro. Tea tree oil gel could be developed as a natural drug to kill ocular D. folliculorum in high-efficency.