As the beauty industry and the world at large become more sustainably driven, you might be looking for ways to reduce your carbon footprint without reducing the overall effectiveness of your makeup, skincare, and haircare routines. While there are many ways to do so—like switching to products housed in sustainable packaging and opting for brands that pay close attention to their carbon emissions—one that often gets overlooked is a simple soap swap.
Curious how switching soaps could lead to a more sustainable routine? Chances are, you haven’t heard of Castile soap. Or, if you have, you’re unaware of what it is—not to mention all of the potential skin and hair benefits it offers. So ahead, discover the endless skin and hair-related uses for Castile soap with the help of board-certified dermatologists Michele Green, MD, and Blair Murphy-Rose, MD.
Meet the Expert
- Michele Green, MD is a board-certified cosmetic dermatologist based in New York City.
- Blair Murphy-Rose, MD is a board-certified dermatologist with Laser & Skin Surgery Center of New York.
What Is Castile Soap?
As the name suggests, Castile soap originated in Castile, Spain. “The original Castile soap was made from pure olive oil and sodium carbonate. However, through the years, the formula has evolved to include other plant-based oils and lye,” Green explains. That’s why, nowadays, shoppers can find Castile soaps made with everything from coconut and walnut oils to almond and hemp. Still, olive oil-based Castile soap remains the most popular.
While many soaps are enriched with oils these days, very few use them as their base. In fact, most soaps are made with tallow (a more ambiguous—and more shoppable—name for animal fat). That’s what makes Castile soap so special. Since it doesn’t use animal fat, Murphy-Rose says that Castile soap is an environmentally friendly, biodegradable, vegetable-based alkaline soap.
The Benefits of Castile Soap
- Gently removes dirt and debris from the skin (as well as other surfaces)
- Ethically produced
- Free of harsh chemicals
In addition to being one of the most eco-friendly soaps that exists, Murphy-Rose says that Castile soap is incredibly hydrating, too. “It both cleanses and moisturizes,” she says, noting that the high glycerin content gives it intense hydration capabilities.
Castile Soap Uses
Thanks to Castile soap’s natural cleansing and hydrating properties, Murphy-Rose says that it works well as a universal facial cleanser. While you can use a store-bought Castile soap as is, a variety of DIY formulas exist, too.
Thanks to its gentle, oil-based nature, Castile soap may work not only as a makeup remover but also for makeup brushes, too. That’s because oils are known for their ability to loosen the grip of stubborn, long-lasting makeup, resulting in both a clean complexion and clean bristles.
The same way it works well as a facial cleanser, Murphy-Rose and Green both say that Castile soap is a great body cleanser as well. This may be particularly true during the cooler months of the year, when you're looking not only to replenish hydration but help lock it in, too.
Another benefit of Castile soap’s rich oil base, according to both Murphy-Rose and Green, is the fact that it provides the perfect amount of protection and glide for shaving. Simply massage a quarter-sized amount onto the area you want to shave and proceed with the process.
Castile soap doesn’t only cleanse the skin, though. Both Green and Murphy-Rose say that it’s suitable as a shampoo, too. So whether you’re looking for a does-it-all product for your next camping trip or simply want to pare down the products in your home, adding a bottle of Castile soap can be extremely worthwhile.
When to Avoid Castile Soap
Given Castile soap’s natural formula, Green says that it’s suitable for just about every skin type. Though, if you have extremely sensitive skin, Murphy-Rose says you may want to hold off. “Castile soap is alkaline and not perfectly pH balanced, so those with sensitive skin or compromised skin barriers may do better with a different cleanser,” she explains. “Still, it is often okay for sensitive skin.”
Skin types aside, Green says that if you have allergies to lye or plant-derived essential oils (which are often added to Castile soap for scent), you may want to steer clear. “Also, if the soap is very concentrated, you may want to dilute prior to use,” she adds, noting that it can make it more tolerable if you do find your skin reacting.
If you plan to use Castile soap as your shampoo, Murphy-Rose says that it’s only suited for those with natural color, as it can strip dyes from strands.
Lastly—and more of a reminder than a reason to avoid Castile soap—Murphy-Rose says that, when mixed with hard water, Castile soap can leave behind a white residue. “If you have hard water, Castile soap may not be the best choice for you,” she concludes.
The Best Castile Soaps
Both Green and Murphy-Rose consider Dr. Bronner's their #1 pick for Castile soap. “It is loaded with vitamin E, organic hemp oil, and jojoba oil, among other natural organic ingredients,” Green says, applauding the gentle, hydrating formula. While the baby version is unscented and arguably the most gentle, Dr. Bronner's has a whole line of liquid Castile soaps, so shoppers can choose from an array of delicious scents like peppermint, lavender, and citrus.
Here we have another of Green's go-tos. This Castile soap is particularly worthwhile for those with sensitive skin, as it's made without fragrance or essential oils—two ingredients that are known to cause irritation for highly sensitized complexions.
This coconut-based Castile soap is infused with olive and jojoba oils to make it incredibly hydrating and smoothing, along with organic aloe vera meant to give it an added soothing effect.
This olive oil-based Castile soap is loaded with a variety of popular ingredients, like willow bark extract, rosehip oil, sunflower oil, and coconut oil. Together, these ingredients promise to gently and effectively cleanse the skin and prevent odors. Additionally, since it's made with antimicrobial ingredients, it makes it an especially great choice for those looking to use Castile soap to tend to dry skin, whether on the body or scalp.
Green also recommends this top-rated Castile soap that you can buy on Amazon. It's sold in four scents and is made with 100 percent plant-based ingredients, making it an especially clean choice for your beauty routine.
The Final Takeaway
Castille soap is a multifunctional cleanser that has a variety of beauty benefits. Outside of beauty, Murphy-Rose shares that Castile soap is suitable as a more sustainable laundry detergent, as well as a household cleaner. In that way, you can think of Castile soap as your one-stop shop for cleaning of all kinds.
Hosokawa K, Taima H, Kikuchi M, Tsuda H, Numano K, Takagi Y. Rubbing the skin when removing makeup cosmetics is a major factor that worsens skin conditions in atopic dermatitis patients. J Cosmet Dermatol. 2021;20(6):1915-1922. doi:10.1111/jocd.13777
Uter W. Contact allergy to fragrances: current clinical and regulatory trends. Allergol Select. 2017;1(2):190-199. doi:10.5414/ALX01604E
Lin TK, Zhong L, Santiago JL. Anti-inflammatory and skin barrier repair effects of topical application of some plant oils. Int J Mol Sci. 2017;19(1):70. doi:10.3390/ijms19010070