What it is

Lavender oil is the essential oil of Lavandula angustifolia, rich in linalool and linalyl acetate. It is common in scalp oils and shampoos.

How it works

In female C57BL/6 mice, 3% and 5% lavender oil applied 5 days a week for 4 weeks increased follicle number and depth, thickened the dermis and reduced mast-cell counts (Lee 2016).

What the studies show

In mice, 3% and 5% lavender oil in jojoba oil raised follicle number, follicle depth and dermal thickness over 4 weeks compared with vehicle. A 3% minoxidil group was included. Lee 2016
No human hair trial of lavender oil alone was found.

How it's used in studies

3-5% in jojoba oil on mouse back skin for 4 weeks.

Side effects and safety

A 2023 review described eight boys with prepubertal gynaecomastia and four girls with premature breast development after exposure to lavender and/or tea tree oil, all resolving after stopping. The authors stress that causation is unproven, since breast tissue often regresses spontaneously, product contents were unclear and skin penetration of the components is limited (Braunstein 2023). Lavender is also a fragrance allergen. Be cautious with children.

Bottom line

Weak evidence. It is pleasant and low cost, but its hair benefit is unproven in humans. Avoid regular use on children.

Studies 2

Lee BH et al. Hair growth-promoting effects of lavender oil in C57BL/6 mice. Toxicol Res. 2016

Design: animal
Duration: 4 weeks
Who: female C57BL/6 mice

Tested: 3% and 5% lavender oil vs vehicle and 3% minoxidil

Result: Follicle number and depth and dermal thickness rose and mast-cell counts fell.

Read the study ↗

Braunstein EW, Braunstein GD. Prepubertal gynaecomastia and premature thelarche linked to lavender and tea tree oil? touchREVIEWS Endocrinol. 2023

Design: review
Who: 8 boys with prepubertal gynaecomastia and 4 girls with premature breast development

Tested: exposure to lavender and/or tea tree oil

Result: All cases resolved after stopping; the authors stress causation is unproven.