Hair Growth Oils Compared: What the Studies Show

Short answer: Rosemary oil has the best human evidence of any scalp oil, and it is still thin. One trial of 100 people with pattern hair loss found it worked about as well as 2% minoxidil after six months. S01 Pumpkin seed oil helped in one small trial, but people took it as a capsule. S02 Peppermint oil has only been tested in mice. S03 Coconut, castor and argan oils have little or no evidence for growth, though coconut oil may help limit damage. S05 S06

This guide compares the most common oils by what was actually studied: who took part, how the oil was used, what was measured and how strong the result is.

What "hair growth" means in these studies

Most of the studies below looked at androgenetic alopecia, also called hereditary or pattern hair loss. A 2025 review calls it the most common cause of hair loss. S07 The two approved medicines for it are topical minoxidil and oral finasteride, which are both prescription medicines according to the review. S07

Other kinds of hair loss behave differently. Alopecia areata, for example, tends to develop quickly and often causes a few bald patches. S10 An oil that helped in one kind of hair loss may do nothing for another. That's why the American Academy of Dermatology says effective treatment begins with finding the cause. S09 If your hair started shedding a few months after an illness, surgery, or rapid weight loss, read about telogen effluvium and hair loss on GLP-1 medicines first.

Hair growth oils compared at a glance

Sources for the table: S01 S02 S03 S04 S05 S06

Rosemary oil

Rosemary oil is the oil most often linked to hair growth, and most of that interest comes from a single 2015 trial. S01 Researchers randomly assigned 100 people with pattern hair loss to rosemary oil or 2% minoxidil for six months. S01

At three months, neither group had a meaningful change in hair count. S01 At six months, both groups had significantly more hair than at the start, and there was no significant difference between them. S01 Scalp itching rose in both groups, but it was more common with minoxidil. S01

The trial had no placebo group, so it can't show how much of the change would have happened anyway. It compared rosemary with the lower 2% strength of minoxidil, and it ran for six months. S01 A 2025 review that included rosemary oil said more robust and long-term data are needed for non-prescription products like it. S07

A Cleveland Clinic dermatologist describes rosemary oil as something that "might help a bit, particularly if your hair loss is just starting," and adds that "there are no guarantees." S08

Pumpkin seed oil

Pumpkin seed oil is often sold as a scalp oil, but the main human trial tested capsules. S02 In that study, 76 men with mild to moderate pattern hair loss took 400 mg of pumpkin seed oil a day or a placebo for 24 weeks. S02

Average hair counts rose 40% in the pumpkin seed oil group compared with 10% in the placebo group. S02 The men taking the oil also rated their improvement and satisfaction higher, and side effects were similar in both groups. S02

This trial was placebo controlled and double blind, which is a stronger design than the rosemary trial. S02 It was still small, it included only men, and it doesn't tell you whether rubbing pumpkin seed oil on your scalp does anything.

Peppermint oil

Peppermint oil's reputation for hair growth rests on a mouse study. S03 Researchers applied saline, jojoba oil, 3% minoxidil or 3% peppermint oil to mice for four weeks. S03 The peppermint group showed the most prominent hair growth effects, including more and deeper hair follicles. S03

This guide found no human trial of peppermint oil for hair growth, so treat it as an early lead rather than proof.

Essential oil blends for alopecia areata

One older trial tested essential oils for alopecia areata, the patchy kind of hair loss. S04 In this 1998 study, 86 people massaged a blend of thyme, rosemary, lavender and cedarwood oils mixed into jojoba and grapeseed oils into their scalp every day. S04 A control group massaged in the carrier oils alone. S04

After seven months, 19 of 43 people (44%) in the essential oil group improved, compared with 6 of 41 people (15%) in the carrier oil group, based on photos reviewed by two dermatologists. S04 The trial was randomized and double blind. S04 It is still one study from 1998, and alopecia areata is a different condition from pattern hair loss.

Coconut, castor and argan oils

These three are some of the most widely used hair oils. A 2022 systematic review of 22 articles looked at whether they help hair growth, hair quality or scalp infestations such as lice. S05

• Coconut oil has been shown to help treat brittle hair and hair infestation, with limited evidence for hair growth. S05 In a lab study, coconut oil was the only one of three oils tested that greatly reduced protein loss from hair when used before or after washing. S06 Sunflower and mineral oil didn't reduce protein loss. S06 The authors worked in the research department of Marico Industries in Mumbai. S06
• Castor oil had weaker evidence for improving hair luster and no strong evidence for hair growth. S05 Our castor oil for hair guide looks at it in more detail.
• Argan oil had no significant evidence for improving hair growth or hair quality. S05

The review also notes that many dermatologists suggest patients keep using these oils because they rarely cause problems, not because they make hair grow. S05 Limiting damage is not the same as growing new hair.

How oils compare with minoxidil

Minoxidil is the over-the-counter treatment most of these oils are measured against. The American Academy of Dermatology says minoxidil can help early hair loss but can't regrow an entire head of hair. S09 Results usually take about 6 to 12 months, and if you stop using it, you lose its benefits. S09

The only head-to-head trial of an oil against minoxidil is the rosemary study above, and it used the 2% strength. S01 The AAD notes that minoxidil tends to work better when used with another treatment. S09

How to use a hair oil safely

Cleveland Clinic offers these tips for rosemary oil, and most apply to other essential oils too: S08

1. Dilute it. Mix a few drops into a carrier oil such as coconut or jojoba to reduce the chance of irritation. S08
2. Apply to the scalp. Oil on the hair lengths won't affect growth. Massage it into the scalp. S08
3. Leave it on. Leave it on for at least a few hours, such as overnight, then wash in the morning. S08
4. Be patient. Plan on two or three times a week for about six months before you judge the results. S08
5. Test first. Try it on a small area of scalp before using it all over, especially if you have fine hair or atopic dermatitis. S08 Our patch test guide walks through the steps.

Using too much can cause scalp irritation, redness, burning and inflammation. S08 Cleveland Clinic also says rosemary oil isn't recommended during pregnancy or breastfeeding. S08 Stop using any oil that irritates your scalp. If you also want to change your wash routine, see which shampoo ingredients for thinning hair have evidence behind them.

When to see a dermatologist

The AAD recommends seeing a board-certified dermatologist to find out what's causing hair loss, because treatment depends on the cause. S09 Some causes, such as low iron, biotin or zinc, show up on a blood test and are treated differently. S09

The limits of the evidence

Rosemary, pumpkin seed and the essential oil blend each rest on one main trial of 100 people or fewer. S01 S02 S04 Peppermint has only animal data. S03 The 2025 review of non-prescription products found improvements in hair density or thickness for several products, including rosemary and pumpkin seed oil, with few side effects. S07 It also said larger, high-quality randomized trials are needed to know how well these products work and how safe they are over time. S07

Frequently asked questions

Which oil is best for hair growth?

No oil has strong evidence. Rosemary oil has the most direct human data for a scalp oil: one trial of 100 people with pattern hair loss found results similar to 2% minoxidil after six months. Pumpkin seed oil also has one small trial, but the oil was taken as a capsule.

Does castor oil make hair grow?

A 2022 systematic review found no strong evidence that castor oil helps hair grow. There was weaker evidence that it may improve how shiny hair looks.

How long does rosemary oil take to work?

In the 2015 trial, neither rosemary oil nor minoxidil changed hair counts at three months. Both groups had more hair at six months. A Cleveland Clinic dermatologist suggests using it two or three times a week for six months before judging it.

Can I put rosemary or peppermint essential oil straight on my scalp?

Cleveland Clinic advises diluting rosemary oil in a carrier oil such as coconut or jojoba, using only a few drops, and testing a small patch of scalp first. Overuse can cause irritation, redness and burning.

Can hair oils replace minoxidil?

There isn't enough evidence to say so. The main rosemary trial was small and short, and topical minoxidil and oral finasteride are the approved medicines for pattern hair loss. A dermatologist can help you find the cause and pick a plan.