Experimental studies have shown that lavender oil, when mixed with a solvent and made into a hair tonic, has a marked hair-growth effect in lab rats, boosting hair follicle number, dermal thickness, and hair follicle depth, resulting in shiny, thick hair. Far from just providing a pleasant scent in hair tonics, lavender is a key ingredient in the pursuit of thicker hair.
Lab tests were done contrasting lavender oil hair tonic with a synthetic minoxidil compound. The positive control of minoxidil has indeed been useful and effective in boosting thick hair, but it can also have negative effects on the spleen when used in hair tonics. In contrast, lavender oil in hair tonic has shown the weight of the spleen to not be significantly different from the beginning of the experiment.