Rosemary oil is believed to improve both hair growth and hair thickness due to its ability to improve cellular generation. In one study rosemary oil is observed to be as efficient as minoxidil but with less itching on the scalp as a side effect.
To use rosemary oil properly, it is suggested to mix several drops of it with carrier oil, and apply it to the scalp area. After ten minutes, it can be washed away normally. This can be done twice per week for best results.