Castor oil is a popular skin remedy that has a long history of use in the African continent. Its use in Western medicine remains limited, but this hasn’t stopped growing online support for the treatment of many skin conditions.
Due to its growing popularity, castor oil has also been touted as a solution to seborrheic dermatitis and dandruff. But is this really the case and is there any evidence to support this.
Review conclusion: Despite historic records citing the use of castor oil in the treatment of seborrheic dermatitis, there is currently not enough modern evidence to support this. And while the anti-inflammatory and occlusive properties may be sufficient to resolve symptoms in mild cases, additional studies would be required.
History/usage of castor oil in skincare
Though there isn’t too much recent research examining the use of castor oil for the treatment of skin disorders, older references can be found :
- The 1929 edition of the Ethiopian Flora Medica (herbal medicine) listed it as a possible treatment for seborrhea of the scalp and tinea infection
- The 1973 edition of the Erboristeria Italiana (Italian Herbal Medicine) recognized castor diluted in an alcoholic solution had anti-seborrheic action and promoted the growth of hair
- Many other claims and uses have been noted all around the world for all sorts of different types of extracts from both the seeds and leaves in the treatment of a variety of skin ailments (the list is quite large and includes warts, eczema, pustules, impetigo, wounds, and ulcers just to name a few)
Despite this long list of possible uses and benefits, modern use of castor oil in skincare mainly focuses on the occlusive, skin conditioning, and viscosity increasing characteristics .
Potential beneficial properties of castor oil
One of the more prominent effects of castor oil appears to be derived from its main constituent, ricinoleic acid. This unique lipid (oil) is abundant in castor oil (nearly 90% of the total composition) and is the primary reason why castor oil has strong laxative effects.
While it may cause diarrhea when ingested, ricinoleic acid has also been shown to have significant anti-inflammatory effects when applied to the skin of mice:
- Effect of ricinoleic acid in acute and subchronic experimental models of inflammation 
- Anti-inflammatory effects of a novel ricinoleic acid poloxamer gel system for transdermal delivery [pubb id=”25542985″]
Unfortunately, it’s difficult to judge how much these effects carry over to humans and just how significant they would be in human trials.
If the effects do carry over, this would offer a suitable explanation to the myriad of beneficial reports from the large variety of skin ailments. After all, the major component of most skin disorders, seborrheic dermatitis included, is the run-away inflammatory response (see the article reviewing the possible causes seborrheic dermatitis for more information).
In addition to anti-inflammatory properties, some papers have noted the potential of ricinoleic acid to act as an antifungal agent:
- In a dental study, castor oil (not fully clear if it was pure castor oil – the study makes mention of castor oil extract and then castor oil detergent) was briefly able to control Candida Albicans growth 
- Some inhibition was noted for a variety of ricinoleic acid derivatives, but the effect was only slight and only presented itself under specific controlled conditions (pH, nutritional availability, temperature, etc) 
But both studies only report marginal effectiveness and cite more effective antifungal solutions to be superior (undecylenic acid is one such option – see notes section).
Many unfounded claims flood the internet
Despite the general lack of scientific evidence (apart from the historic reports cited above) to support the use of castor oil in skin disorders, the internet is full of such claims. It’s touted as a remedy for a wide list of ailments and is reported to have miraculous results.
Unfortunately, many of these claims either fail to cite references or blatantly skew the study outcomes to support their statements. For example, it’s common to see castor oil being promoted as the magic solution to dandruff, eczema, hair loss, and even psoriasis. Yet, there aren’t any studies that support any single one of these claims (please let me know if you find anything in the comments).
Possible merits of castor oil for the treatment of seborrheic dermatitis
Based on the evidence presented, its difficult to presume that the anti-fungal properties of castor oil would be substantial enough to explain its historic use in the treatment of seborrheic dermatitis.
What we do know, is that seborrheic dermatitis is not strictly driven by fungi on the skin surface. More-so, it is our immune system’s out-of-sync response which triggers the symptoms. And these symptoms include inflammation, skin barrier disruption, dryness, and the drastic increase of oxidized lipids on the skin surface which characterize the condition.
So while castor oil may not best fit for all the parameters of the condition, the anti-inflammatory and occlusive properties of castor oil could potentially explain some of the success reported. And for some people, the relief of these symptoms alone may provide enough support to allow for the runaway immune system to stabilize.
- As easy it is to theorize possible effects, the real-life outcomes are much harder to predict due to a large number of variables
- Undecylenic acid (common in creams for foot fungus) can be produced by heating ricinoleic acid under vacuum and is a much more potent antifungal agent 
- Numerous allergic reactions to castor oil have been reported [7, 7, 8]
- The Latin name for the castor oil plant is Ricinus communis
- Lab studies have demonstrated leaf extracts have both antioxidant and anti-inflammatory effects, but these are not widely available [9, 10]
Castor oil appears to be one of those strange herbal remedies that have a lot of claims and support plastered around the internet; yet, the evidence to support its use is hard to come by.
Given the current state of evidence, it would be difficult to recommend the use of castor oil in the treatment of seborrheic dermatitis. While it may provide some anti-inflammatory support and occlusion, several more documented options exist: such as crude honey, tea tree oil, and even salt (while not optimal, these still have significantly more evidence behind them).
If you’ve already attempted to use castor oil and have some personal experience with its effectiveness, would love to hear more in the comments section below. Questions, suggestions, and corrections are also welcomed.