Humans have always rubbed oily substances on our skin. If you look back across history, many cultures used moisturizers in ancient times to protect their skin and keep it soft. Caring for our bodies is instinctual and skincare falls somewhere in the middle of beauty ritual and health.

There is no argument that can be made against the profound impact that moisturizers have on skin health. They lock in moisture and restore hydration so various cell processes can occur, they help our skin barrier, and they can even help the skin heal faster. But the modern day moisturizer has evolved from what we’ve seen in the records of ancient Egyptians.

Nowadays, moisturizers are sophisticated emulsions that combine oil and water phases. The emulsifiers used available allow for cosmetically elegant textures and an enjoyable consumer experience. Moisturizers not only combine an array of moisturizer ingredients like emollients, occlusive agents, and humectants but can act as a vehicle for UV filters or other ingredients.

Yet instead, TikTok and other social media platforms are bringing us back to the past with castor oil and tallow (rendered animal fat).

Ingredient Composition

If we look at what makes up tallow and castor oil, it’s not very exciting. While a well formulated moisturizer will often contain emollients like these, they don’t just stop there.

Castor Oil Composition1

• 90%+ ricinoleic acid
• 4% linoleic acid
• 3% oleic acid
• 1% stearic
• >1% linolenic fatty acids

Tallow Composition 2

• 30-50% oleic acid
• 26% palmitic acid
• 14% stearic 
• 4% linoleic and linolenic acids

Note: fatty acid profiles can vary depending on season and crop for plant oils, the animal used for tallow, or how they were measured 

As mentioned, both tallow and castor are emollients. This means they can help soften the skin surface and help with dry skin. Their composition also suggests that they may be occlusive, or moisture trapping.

The ricinoleic acid in castor oil may be responsible for some of its purported benefits which we will discuss next. However, tallow contains a high concentration of oleic acid which has been shown to be disruptive to the skin barrier3 and other oils like olive oil that are predominantly oleic acid have demonstrated this.

What the Science Says

The evidence for both of these popular TikTok trends is sparse, making it difficult to recommend seeking them out either as standalone products or in skincare.

Tallow

• emollient and likely occlusive
• worked well in a moisturizer in one study5

Castor Oil

• emollient and likely occlusive
• improved the under eye in a small, limited clinical trial6
• may be antimicrobial and anti-inflammatory but topical studies needed

There are some wild claims around these ingredients but there is no reason to suggest that either can replace Botox and erase fine lines - or add volume back to the face l. Meanwhile, skincare ingredients like the retinol in Stratia Skin Night Shift have decades of research.

The takeaway:  Both of these ingredients need further research on human skin before they can be recommended and you’re best served just finding a well formulated moisturizer that works for your skin.

References 

1. https://pubchem.ncbi.nlm.nih.gov/compound/Castor-Oi
2. https://nap.nationalacademies.org/read/22/chapter/14?chapselect=yo&Jump_to_Specified_Page_x=0&Jump_to_Specified_Page_y=0#203
3. https://pubmed.ncbi.nlm.nih.gov/24372651/
4. https://pubmed.ncbi.nlm.nih.gov/22995032/
5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11193910/
6. https://onlinelibrary.wiley.com/doi/full/10.1111/jocd.16056
7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8837976/

Mira is a skincare educator, blogger, and the content creator behind Skin Science by Mira and The Skincare Forum on Facebook. While skincare keeps her busy, she’s also pursuing her degree in Nursing and loves to spend her free time hiking.  As a content writer for Stratia Skin, Mira shares her evidence-based approach to skincare topics and a passion for making science accessible.