Castor oil has one of the longest continuously documented medicinal histories of any remedy in this Atlas, referenced in the Ebers Papyrus, an ancient Egyptian medical text dating back over 4,000 years, where it was used both medicinally and as lamp fuel. Its use for hair and skin care in hot, dry climates persisted across Egyptian and later broader African and Middle Eastern traditions for millennia.
Castor oil's modern reputation has expanded considerably beyond its historically-grounded uses into a wide range of popular claims — hair regrowth, "detox," joint pain, and more — making it a genuinely useful case for separating its one well-established traditional use from the much larger body of less-supported modern claims attached to it.
Castor oil has exactly one traditional use with real, longstanding recognition: short-term relief of occasional constipation, via a well-understood mechanism (its ricinoleic acid content stimulates intestinal contractions). This use is genuinely old and mechanistically sound enough that castor oil is still used clinically today to clear the bowel before certain medical imaging procedures — a real, if narrow, modern application.
Beyond constipation, the evidence for castor oil's other popular claims is consistently described as weak across multiple independent clinical review sources. For hair growth specifically — probably its most searched-for modern use — reviewer after reviewer states plainly that there is "no strong clinical evidence," "no solid clinical evidence," or "little clinical evidence" that castor oil stimulates hair growth on its own. One 2025 trial did find a castor oil *blend* (combined with rosemary oil) improved hair growth measures compared to coconut oil — but this is combination-product evidence, not proof of castor oil's individual contribution. Given one well-grounded but narrow traditional use and consistently weak evidence for its broader popular claims, "Limited" reflects the honest overall picture.
Cold-pressed from castor beans; taken orally in small doses for short-term constipation relief, or applied topically to skin and hair.