How Castor Oil May Help With Hair Growth, According to Experts (2025)

If it seems like with each birthday you’ve noticed more hair in your brush and shower drain and less on your head, know that you’re not alone. More than half of women 50 and older deal with some degree of thinning hair. And while there are many factors linked to hair loss, including stress, hormonal fluctuations and genetics, there’s one natural, inexpensive ingredient that may help your thinning hair: castor oil. Here, we get into all the benefits of castor oil for hair, how it can help with hair growth and more.

What is castor oil?

Castor oil is extracted from the beans/seeds of thericinus communisplant. The oil has been used traditionally for a variety of medicinal purposes. When ingested it serves as a stimulant laxative, and when used topically, it has skin-healing properties known to aid in wound repair and is beneficial for treating skin conditions like dermatitis and fungal infections. And fortunately, the oil has also been found to help with hair growth.

How castor oil helps regrow hair

“Castor oil contains ricinoleic acid, a monounsaturated fatty acid, which has moisturizing and antibacterial properties,” explains Kiran Mian, DO, a dermatologist at Hudson Dermatology and Laser Surgery in New York City. Keeping hair hydrated is key as this fortifies hair follicles to prevent breakage, which can lead to hair thinning. And antibacterials kill fungus and ease inflammation on the scalp (these can both lead to excessive shedding), creating a healthy environment for hair to grow and limiting fallout.

Plus, since the oil has a high ricinoleic acid content (roughly 90 percent), it may improve blood flow to hair follicles, says Rahi Sarbaziha, MD, a board-certified integrative aesthetics doctor based in Beverly Hills who specializes in anti-aging treatments. This is beneficial as a boost in blood flow delivers oxygen and nutrients to follicles that promote hair growth.

However, there is little scientific evidence that castor oil can directly help regrow hair. “While the clinical evidence for castor oil helping hair growth is lacking, anecdotally we do hear of improvement in hair fullness, decrease in shedding and improvement in hair length with consistent use,” adds Dr. Mian. In fact, one study found that castor oil improved hair’s natural luster, which in turn causes hair to appear fuller.

How to use castor oil to help hair growth

One of the best parts about castor oil is that it’s fairly simple and easy to use, and won’t break the bank.

First, find a quality castor oil, often available at the drugstore or on Amazon. Then, Dr. Mian recommends applying a small amount of oil (2 tsp. should suffice) onto a dry scalp in the areas you notice the most hair loss/thinning and gently massage it in with your fingertips (this will further improve blood flow to the scalp to stimulate growth). It’s also beneficial to apply any leftover oil (or add extra castor oil if you need more) to the mid-lengths to ends of hair. This will help condition and nourish dry hair, and help prevent breakage.

After the oil is applied, cover your head with a shower cap and leave it on for 4 hours (or apply before going to bed and lay an old towel over your pillowcase to protect it from staining), then rinse out with shampoo. Repeat one time per week.

Tip: Combining three drops of rosemary oil with castor oil before applying on the scalp can also add to the hair-thickening benefits. That’s because the rosemary oil’s rosmarinic acid has been found to increase circulation to the scalp to spur new growth.

Watch the video below to see how one woman used castor oil to thicken her hair:

Other benefits of castor oil for hair

As mentioned, castor oil’s antibacterial properties can help fight off fungus on the scalp, which can lead to dandruff, flaking, dryness and more. A poor scalp environment often means poor hair growth.

Castor oil can also add shine to and moisturize dry locks. This is thanks to its ricinoleic acid, rich in fatty acids. If you use a lot of heat on your hair, spend a lot of time in the sun or just have a drier hair texture naturally, castor may help nourish your strands.

Castor oil can regrow hair on eyebrows and eyelashes

Even though the hair growth cycle for eyebrows and eyelashes is different from the growth cycle of hair on the head, these hairs still “need hydration, antioxidants and moisture just like our scalp hair,” says Dr. Mian. And applying castor oil to brows and lashes can offer results quicker as the oil’s fatty acids absorb faster into these thinner hairs, plumping them instantly for a fuller look.

To apply castor oil onto brows and lashes, simply dip a clean spoolie brush into the oil and brush onto clean, dry hairs once a day. “Using at nighttime will avoid interactions with makeup and external pollutants,” advises Dr. Sarbaziha. “You can leave it on for anywhere from one hour to overnight for maximum benefit.” Repeat nightly to see lasting results within 30 days. Note: If using before bed, place an old towel over your pillow as the oil can stain.

For an eye doctor’s take on how using castor oil is beneficial (and safe!) for eyelashes, watch the YouTube video below from Dr. Rupa Wong.