Rosemary (Rosmarinus officinalis) has a long history of traditional use as a hair tonic, particularly in Mediterranean cultures. It has been employed in folk remedies to support scalp health, promote hair growth, and reduce dandruff. Rosemary oil is often massaged into the scalp or added to shampoos and hair rinses. The traditional rationale is that rosemary may stimulate circulation in the scalp, thereby encouraging hair growth and improving hair quality.

Scientific studies investigating rosemary's effects on hair growth are limited and mostly preliminary. A notable small-scale study published in 2015 compared rosemary oil with minoxidil (a standard treatment for androgenetic alopecia) and found that both groups experienced increased hair count after six months, with rosemary oil users reporting less scalp itching. However, the study's sample size was small, and further research is required to confirm these findings. Other research has explored rosemary's anti-inflammatory and antioxidant properties, which could theoretically benefit scalp health, but conclusive evidence for direct benefits on hair growth or prevention of hair loss is lacking.

In summary, the use of rosemary for supporting hair and scalp health is primarily supported by traditional practice, with only limited and low-quality scientific evidence suggesting potential efficacy. More robust clinical trials are needed to validate its use for this purpose.