Rosemary oil is affected by blood circulation and skin health. It also performs as well as minoxidil, a common hair growth treatment but with less scalp itching as a side effect.
Rosemary Oil helps reduce stress levels and nervous tension, boost mental activity, encourage clarity and insight, relieve fatigue, and support respiratory function. Improves alertness, eliminates negative moods and increases the retention of information by enhancing concentration. The scent of Rosemary Essential Oil stimulates the appetite and is also known to reduce the level of harmful stress hormones that are released when involved in intense experiences. Inhaling Rosemary Oil boosts the immune system by stimulating internal anti-oxidant activity, which in turn fights ailments caused by free radicals, and it relieves throat and nasal congestion by clearing the respiratory tract. Inhaling rosemary oil increases concentration and memory. 
Add 5-25 drops to 10 ml of carrier oil for local application.
Add 4-12 drops to a bowl of steaming water/facial steamer and inhale deeply for 5-10 minutes.
For massage, add 2 drops to 20 ml of carrier oil.
For diffusing, add 10-15 drops to a diffuser.
Start with the lowest number of drops; increase as desired.
Mix several drops of rosemary oil with olive or coconut oil and apply it to your scalp. Leave it in for at least 10 minutes before washing it out with shampoo.