Does Castor Oil Grow Eyebrows? The Facts

If you have spent any time on social media or in natural beauty circles, you have likely seen the claim that castor oil can make your eyebrows grow thicker, darker, and faster. The short answer is this: there is no solid clinical evidence that castor oil directly causes eyebrow hair growth. What little research exists focuses on scalp hair, not eyebrows, and the results are mixed at best. The belief comes from the oil’s chemical properties and a lot of anecdotal reports, but science has not backed it up in any meaningful way. This article walks through what is actually known, what is probably hype, and what might help if you are trying to grow your eyebrows.

What Is Castor Oil and Why Do People Think It Works?

Castor oil comes from the seeds of the Ricinus communis plant. The main active ingredient is ricinoleic acid, a type of fatty acid that makes up about 90 percent of the oil. The theory behind castor oil for hair growth centers on this acid.

Ricinoleic acid is known to have anti-inflammatory properties. Some people argue that a healthier scalp or brow area, free from inflammation, supports better hair growth. That idea makes sense in theory. But there is a big gap between reducing inflammation and actively stimulating a hair follicle to grow.

Another common claim is that castor oil blocks a hormone called dihydrotestosterone (DHT), which is linked to hair loss. This claim comes from a single 2002 laboratory study where ricinoleic acid showed weak DHT-blocking activity in a test tube. No human studies have confirmed this effect. Applying oil to your eyebrows is not the same as a drug that blocks hormones in your bloodstream.

Most of the enthusiasm comes from personal stories. People online share before-and-after photos and swear by their results. These stories are not controlled experiments. You cannot tell if the growth happened because of the oil, a change in diet, less stress, or just normal hair cycling. Anecdotes are useful for generating ideas but not for proving effectiveness.

Does Castor Oil Grow Eyebrows? What the Research Actually Shows

As of 2026, there are no peer-reviewed studies specifically testing castor oil on eyebrow hair growth. None. The closest research comes from a few studies on scalp hair, and those results are not encouraging for castor oil fans.

A 2015 study published in the Journal of Cosmetic Dermatology tested a product containing several plant oils, including castor oil, on hair growth in mice. The mixture showed some effect, but the study could not isolate whether castor oil was responsible. Mouse skin is also very different from human skin.

A 2021 review in the International Journal of Trichology looked at natural oils for hair growth. The authors noted that while castor oil is widely promoted, there is “insufficient clinical evidence” to recommend it for hair growth. They pointed out that most claims rely on tradition and marketing, not data.

The American Academy of Dermatology does not list castor oil as a treatment for hair loss or thinning. The FDA does not regulate it as a drug for hair growth. When a treatment has no clinical trials, no regulatory approval, and no support from major medical organizations, the honest conclusion is that the evidence is absent.

This does not mean castor oil is useless for everyone. It means you should not expect it to work like a proven treatment. If you try it and see results, it could be real for you, but it could also be a placebo effect or coincidence.

What Actually Causes Eyebrow Thinning or Sparse Growth?

Before trying any treatment, it helps to understand why your eyebrows might be thin. The cause often determines what will actually help.

Overplucking or waxing is the most common cause. Repeatedly pulling hairs out can damage the follicle over time. In some cases, the damage is permanent. The follicle stops producing hair entirely.

Aging naturally reduces hair density everywhere, including eyebrows. Hair follicles shrink and produce thinner, shorter, and lighter hairs as you get older.

Medical conditions can cause eyebrow loss. Hypothyroidism is a common one. The thyroid gland does not produce enough hormone, and hair thinning is a classic symptom. Alopecia areata is an autoimmune condition where the immune system attacks hair follicles. Eczema or contact dermatitis on the brow area can also cause temporary loss.

Nutritional deficiencies play a role for some people. Low iron, zinc, biotin, or vitamin D levels can affect hair growth. But if your diet is balanced, adding more of these nutrients will not make your eyebrows grow faster.

Chemotherapy causes temporary hair loss everywhere, including eyebrows. Hair usually grows back after treatment ends, but the texture and density may change.

If your eyebrow thinning is sudden or patchy, see a doctor. It could be a sign of an underlying health issue that needs treatment. Castor oil will not fix a thyroid problem or an autoimmune condition.

Comparing Castor Oil to Proven Eyebrow Growth Options

There are only a few treatments with actual evidence behind them for eyebrow growth. The table below shows how castor oil stacks up against options that have been studied.

Bimatoprost is the only FDA-approved treatment for eyelash growth, and it is often used off-label for eyebrows. Studies show it increases length, thickness, and darkness of lashes significantly. Eyebrow results are similar, though less studied. Minoxidil is widely used off-label for brows, but the evidence is mostly from scalp research and case reports.

Castor oil sits at the bottom of this list for a reason. It has no clinical data behind it. That does not mean it cannot work for some people, but it means you should not choose it over a proven option if you want reliable results.

What to Avoid When Trying to Grow Your Eyebrows

Many products and habits marketed for eyebrow growth are a waste of money or even harmful. Here is what to watch out for.

• Serums with prostaglandin analogs that are not FDA-approved. These can cause permanent darkening of the iris and loss of fat around the eye area. Only use products with bimatoprost or similar ingredients under medical supervision.
• Essential oils like peppermint or clove oil applied directly to brows. These can cause burns, blistering, and scarring. Never apply undiluted essential oils to your face.
• Hair growth supplements that promise eyebrow results. Most contain biotin, which only helps if you are actually deficient. The NIH states that biotin deficiency is rare in the US. Excess biotin is excreted in urine and does nothing for hair.
• Over-exfoliating the brow area. Scrubbing or using chemical exfoliants can irritate follicles and cause hair to fall out. Gentle cleansing is enough.
• Wearing heavy brow makeup daily and not removing it gently. Tugging and rubbing can break hairs and damage follicles over time.
• Believing any product that says “clinically proven” without checking what that actually means. Many companies run tiny, unblinded studies that would not pass peer review. Look for studies with at least 50 participants, a control group, and publication in a reputable journal.

The supplement industry is especially bad about this. A 2023 investigation by ConsumerLab found that several popular hair growth supplements did not contain the amounts of ingredients listed on the label. Some contained none at all. Your money is better spent on a blood test to check for real deficiencies.

Practical Steps If You Still Want to Try Castor Oil

If you understand the limits of the evidence and still want to try castor oil for your eyebrows, there is likely no harm. Here is how to do it safely.

Use cold-pressed, hexane-free castor oil. Hexane is a solvent used in some extraction processes, and you do not want it near your eyes. Organic is fine but not required. The purity matters more than the label.

Apply a tiny amount to clean, dry brows. A clean mascara wand or a cotton swab works. One drop per brow is enough. Too much oil can run into your eyes and cause blurry vision or irritation.

Do it once daily, preferably at night. Leave it on for at least a few hours. Some people leave it on overnight. Wash it off in the morning with a gentle cleanser.

Be patient and realistic. Hair grows slowly. Eyebrow hairs have a growth cycle of about 4 to 6 months. If you see no change after 6 months of consistent use, it is probably not working for you.

Take a photo in the same lighting every month. This gives you an objective record. Our memories are unreliable. What feels like growth may just be better grooming or lighting.

Stop using it if you develop redness, itching, or bumps. You could be having an allergic reaction or clogging your follicles. Give your skin a break and see if the irritation clears.