Rosemary oil can burn the skin; therefore, you should never apply it directly on your scalp without diluting it. Do not use it on already dirty hair. You should use it on clean hair and scalp.
Rosemary oil is rather applied on the scalp rather than the hair, and it helps boost the flow in the capillaries of the scalp.
Rosemary oil activates the pores, helps strengthen the hair roots, and helps the hair strands to grow thicker and healthier.
Add one or two drops of rosemary oil to fixed oils such as olive oil and sesame oil, and apply the mixture on the hair roots. If you use undiluted rosemary oil on your scalp, it will cause irritation, burning and dryness on your hair roots.