Castor Oil vs. Rosemary Oil for Hair Growth: What the Science Actually Says

If you've spent any time in natural hair spaces online, you've seen both of these oils held up as growth miracles. Castor oil has been a staple in Black hair care for generations. Rosemary oil exploded in popularity after studies started comparing it to minoxidil.

But how do they actually work? And do you have to choose?

Castor Oil: What It Does (and What It Doesn't)

Castor oil is thick, heavy, and deeply moisturizing. It's rich in ricinoleic acid, a fatty acid with demonstrated anti-inflammatory properties. It also coats the hair shaft to reduce breakage and moisture loss, and when massaged into the scalp, it increases blood circulation to the hair follicles.

What castor oil doesn't do is directly stimulate new hair growth at the follicle level. What it does do is create better conditions for the hair you already have — less breakage, better scalp health, more retained length. For naturals dealing with dryness, brittleness, or slow length retention, this matters enormously.

The downside: it's very thick. Too much, too often, leads to buildup on the scalp. Use it sparingly — a little goes a long way.

Rosemary Oil: What the Research Shows

Rosemary oil has been studied more directly as a hair growth stimulant. A 2015 study published in SKINmed compared rosemary oil to 2% minoxidil (the active ingredient in Rogaine) over six months and found comparable results in hair count — with less scalp itching in the rosemary group.

The mechanism is similar to minoxidil: rosemary improves circulation to the scalp and has been shown to inhibit DHT (the hormone linked to androgenic hair loss) from binding to receptors. This makes it particularly relevant for people experiencing thinning at the hairline or crown.

The key with rosemary is consistency. It's not a quick fix — the study ran for six months. But used regularly, the evidence is more robust than almost any other natural hair growth ingredient.

So Which One Should You Use?

Both — they do different things, and they work better together than apart.

Castor oil creates a healthier foundation: less breakage, better moisture retention, improved scalp circulation through massage. Rosemary oil targets the follicle more directly, stimulating growth and potentially slowing loss.

Our Castor + Rosemary Nourishing Hair Oil was formulated around exactly this pairing. You get the sealing and moisture-retaining power of castor oil with the follicle-stimulating properties of rosemary, in a formula that's balanced enough to use without weighing your hair down.

How to Use It

Warm a small amount between your palms and massage into the scalp for 3–5 minutes — this is important, the massage itself increases circulation and amplifies the effect of both oils. Apply any remaining to the length of your hair as a sealant after your leave-in. Use 2–4 times per week for best results.

Consistency over time is what creates results with any oil. Give it at least 8–12 weeks before evaluating.

Ready to try it? Shop the Castor + Rosemary Hair Oil — or build your full routine with the rest of our sulfate-free, paraben-free line.