Study aim: Determine the effect of topical Henna oil on pain in chronic sciatica patients Design: A randomized controlled clinical trial with parallel groups, double blinded Settings and conduct: The research site is the neurosurgery clinic of Imam Khomeini Hospital and the health centers affiliated to the Faculty of Iranian Medicine of Tehran University of Medical Sciences. Chronic sciatica patients are randomly divided into 3 groups of henna oil(in sesame oil base), sesame oil and placebo. Patients in 3 groups use 10 drops of the oil or placebo, 3 times a day, for 4 weeks, topically on the low back and unilateral painful area from gluteal to middle posterior of thigh; and they can take one diclofenac 25 mg tablet up to 2 times a day, If they have severe pain. Patients and researchers are not aware of treatment allocation. Participants/Inclusion and exclusion criteria: Inclusion criteria: Chronic unilateral sciatica pain for at least 3 months and more؛ age 18 to 65 years; Pain score of 1 or more on visual analog scale; Willingness to participate in the study; Without communication problems; Not being candidate for surgery; No history of surgery in the low back; No history of alcohol and narcotic abuse; Body mass index between18.5 to 34.9 Exclusion criteria: Pregnancy or lactation; Severe allergy to any of the medications used in the study; Severe side effects; Unwillingness to continue participating in the study; No use of oils more than twice in a row; Acute illness or accident during the study; G6PD; Aggravation of pain; Use of other complementary and alternative therapies; Use of analgesics out of the study؛ Cauda equine syndrome; Symptoms require further investigation Intervention groups: Intervention group1: To use topically henna oil(in sesame oil base); Intervention group2: To use topically sesame oil; The Placebo group: To use topically mineral oil Main outcome variables: Pain intensity