Background: Onosma dichroanthum Boiss. belongs to the Boraginaceae family and is one of the most important medicinal plants in north of Iran. This study aimed to examine the effect of the petroleum ether root extract ointment of Onosma dichroanthum Boiss. on healing of a surgically induced open skin wound in rats.

Materials and Methods: In this study, 54 male adult Wistar rats were randomly allocated into control, vehicle, and experimental groups. A 20-mm cephalocaudal incision was made on the back skin of rats. Rats were sacrificed on days 4, 7 and 14 and histological examination (the number of fibroblasts, neutrophil, blood vessel sections and thickness of epiderm) was performed on skin samples.

Results: On day 4, the number of fibroblasts was significantly increased in the experimental group compared to the vehicle (P<0.003) and control (P<0.001) groups. On day 7, no significant difference was seen in the number of fibroblasts in the experimental group compared to the vehicle group (P<0.680) and fibroblasts were significantly increased in the experimental and vehicle groups compared to the control (P<0.001). On day 14, fibroblasts were significantly increased in the experimental and control groups compared to the vehicle (P<0.001) and there was no significant difference in the number of fibroblasts in the experimental group compared to the control (P<0.843). Also, no significant difference was seen in the number of neutrophils, blood vessel sections and thickness of epiderm on days 4, 7 and 14 among the groups.

Conclusion: Topical application of the petroleum ether root extract of onosma dichroanthum Boiss. has no significant effect on the healing of skin wound in rats.