Short answer? Maybe. “There’s no published data showing that castor oil can help, but I do have the occasional patient who swears by it,” notes board-certified dermatologist Whitney Bowe, M.D., about castor oil for hair growth. Perhaps because “it depends on the length of the anagen (or growth) phase of your hair to begin with,” board-certified dermatologist Jeanine Downie, M.D. previously told mbg. Meaning, those with a naturally longer brow growth phase may see profound benefits from using castor oil. For others? Meh, not really.

Even without clinical data, though, it makes sense why some do see success: Castor oil’s antioxidant and fatty acid content feeds the delicate brow hairs with nutrients, which can help combat free radical damage and inflammation (and for what it’s worth: both are linked to hair aging and hair loss).

Castor oil is also incredibly moisturizing—it’s both an emollient and an occlusive, which means it penetrates the strands with ease as well as seals in moisture. (This is also great news for your eyebrows, as moisturized brows do tend to grow fuller.) Keeping the strands happily doused in moisture is crucial for staving off hair loss as well, so even if the famed oil doesn’t cause growth, per se, it can keep the wisps you do have healthy. 

So, what’s the verdict, you ask? We still can’t say whether coating your brow hairs with castor oil will, without a doubt, help them grow fluffy and full. There’s no clinical research to back up the claims—no matter how striking some people’s results may be—but the specific compounds and properties of castor oil do carry some scientific weight. And as board-certified dermatologist Ava Shamban, M.D., founder of SKINFIVE, tells mbg, “There is no denying its anecdotal powers and prowess.” 

https://www.mindbodygreen.com/articles/castor-oil-for-eyebrows-does-it-help-them-grow-how-to-apply-it