What Can You Mix with Castile Soap?

Over the years I have received an extraordinary range of questions about mixing stuff with our Castile soaps. There’s a lot of creative thinking going on out there.

But before you get busy with your green self, let me remind you:

Chemistry happens.

I know that you want to toss together your favorite Green-It-Yourself (GIY) ingredients and hope everybody gets along. But sometimes they don’t.

I am not a fan of complicated mixtures. I don’t do complicated. Just give me some Castile soap with an occasional dash of baking soda or essential oils and send me on my way. However, just because I’m not a fancy girl, don’t let me hold you back.

Helping me here is Dr. Vartan Libaridian, Dr. Bronner’s chemistry and R&D consultant. The chart below gives you both my lay analysis and Dr. Vartan’s scientific breakdown.

 Bronner MomDr. Vartan
Aloe Vera
If you picture “aloe vera” as an enticing green gel, you have been grossly misled. The real thing is slimy and turns mustard yellow and stains like nobody’s business. That being said, pure aloe applied to skin straight from a plant provides highly effective sunburn relief. However, when I combined the Castile with just a bit of the pulp inside my aloe frond, it gelatinized the whole amount of soap. Think “mucousy.” Very unappealing. Better to apply aloe vera after you wash.
Aloe vera has at least 75 active ingredients including saponins, vitamins, amino acids, salicylic acid. However, adding this material either in powder or in solution (gel) form to the liquid soap does not give the soap any added value. The brief contact of the liquid soap with aloe vera on the skin will not leave any aloe residue, and aloe requires prolonged contact to do its work.
Baking soda
Baking soda adds a soft abrasion to the cleaning power of the soap, which makes it a good scrubber for grimy sinks and laundry. In laundry, it is a whitener and deodorizer. It also buffers the Castile soap, protecting it from acidic substances that might affect its pH.
Bleach
I don’t know why you would want to combine the Castile soap with bleach. If you’re using the Castile in an effort to be safer, you’re undoing that effort by adding bleach, which causes everything from obstructive lung disease to burns to environmental contamination.
Hypochlorite                 Soap
NaClO     +          R-(CH2)n-COOK
pH 12-13.                   pH 9-9.5

When blended, Na [sodium] displaces K [potassium], thus creating R-(CH2)n-COONa . This is a hard soap formula. This doesn't last too long, and eventually it dissolves. In summary, the soap stays as soap, with both K and Na soap coexisting, but at a higher pH.  It can be irritating to the skin.
Borax
Borax is an effective cleaning agent, but I don’t like it. Combining it with Castile soap doesn’t change this. Borax is praised because it is sustainable and biodegradable and old. But it is not non-toxic. It is irritating to the skin, dangerous if inhaled, and has been linked to reduced sperm count in men and reduced libido in women. It should be kept well away from children and gloves should be worn when handling it.
Borax may have some beneficial effects when combined with Castile soap. It has a pH of 
9.3, similar to that of the soap. It buffers the Castile soap, protecting it from acidic substances that would break it down, thus helping the cleaning process. 
Castile SoapCombining Castile soaps is a fantastic thing to do to achieve your perfect scent. All the soaps in our Castile line have the same soap base with different essential oils added, except for the unscented, which has a higher ratio of saponified olive oil. My dad had his “Euco-Peppo Bear Wash,” a blend of Dr. Bronner’s Peppermint and Eucalyptus which he used for washing our dogs. A favorite blend of mine is Citrus & Almond.
Coconut milk
This combo is all about making a more moisturizing shampoo. It does reduce the cleaning ability of the soap because some of the soap molecules are busy chasing the oil molecules in the milk, but there can still be some cleaning power available. See notes on “Oil” below.
Club Soda
I’m not really sure of the goal of combining this with castile. Maybe because I suggest using club soda to clean windows. Once again it’s the idea that if each are good then both together must be better. Not really though.
Total waste of money and time. The addition of carbonated water at pH 3-4 with soap will release Carbon Dioxide. Nothing else. Bubbling soap. Very unstable. 
Epsom SaltEpsom salt is magnesium sulfate and has a range of therapeutic benefits. However, it is slightly acidic, which brings us back to the idea of acid/base reactions. (See my post, A Word of Caution About Vinegar & Soap.) Soap is a base, aka an alkali. Because of this Epsom salt does react with Castile soap. It is not a dangerous reaction, but it undoes the benefit of both substances. Use them separately. Not together. Epsom salt is not compatible with Castile soap. Magnesium sulfate (Epsom salt) has a slightly low acidic pH, around 6. The Castile soap has a pH of around 9. Adding the magnesium sulfate reverses the soap and releases the fatty acid, producing visible flakes of oil.
Essential OilsEssential oils have a lot to add to cleaning solutions both for personal care and for house care. They can give you a personalized scent and add therapeutic qualities. Avoid the trap of thinking that if a little is good, then more is better. Some essential oils are pretty potent. Do research on each type, as they have very distinctive properties.
Any essential oils can be added. They might cloud out the Unscented Baby Mild Soap.
Glycerin
Whether you’re looking to thicken the soap or make it smoother, keep in mind that the soap already has naturally occurring glycerin in it. More glycerin doesn’t increase the efficacy of the soap, but if it makes you happy, go for it.
Adding glycerin increases moisturization potential of the soap, but above 2-3% it decreases foaming properties.
Hydrogen peroxide
Hydrogen peroxide is a little misleading, all coy and subdued in its modest brown bottle. It’s a mild antiseptic on cuts and has an abundance of other uses. But when a chemist uses the word “explosive”…

Combining these two doesn’t boost the effectiveness of either. Another myth of thinking if both are good, together they’d be better. They’re not.
This material can be dangerous if the customer uses concentrated hydrogen peroxide (30% concentration or higher). Mixed with castile soap, it releases oxygen. If there is a heat source next to it, it can be explosive. Usually, the hydrogen peroxide that is used to clean wounds is at 3% concentration. In this case, the danger is minimal. When mixed with the soap, the hydrogen peroxide brings no antibacterial benefit. Hydrogen peroxide is acidic so any contact with alkaline soap will cause it to dissociate into water and oxygen.  You are basically destroying the peroxide molecule. 
Oatmeal
I am intrigued by the discussion of oatmeal face masques, dry shampoo, and exfoliators. I had no idea. There is no problematic reaction in blending oatmeal with Castile soap. My only concern is clogging the plumbing. If I do try a face masque or some such, I’ll rinse it off in the kitchen with the garbage disposal.
Oil - Jojoba, olive, or coconut The idea here is to make the soap more moisturizing. I get that. But keep in mind that soap grabs hold of oils. This is its primary purpose. So if you add too much of any oil, then the soap is going to be busy chasing the oil you’ve added instead of the grime on your body. Per Dr. Vartan’s analysis, add no more than ¼ - ½ tsp (1.25-2.5 mL) per 1 cup (250 mL) of soap. For deeper moisturizing, wash with the soap and moisturize afterwards.Any of these oils can be added.  They make the soap superfatted, which means it contains oil that has not been turned into soap. More than 0.5% – 1% is not recommended.
OxycleanThis is another effort to give the castile an added boost. Oxyclean is a combination of hydrogen peroxide (see above) and washing powder (see below). Might as well just reach for the washing powder.
This is another effort to give the castile an added boost. Oxyclean is a combination of hydrogen peroxide (see above) and washing powder (see below). Might as well just reach for the washing powder. Oxyclean contains hydrogen peroxide and sodium carbonate. Hydrogen peroxide as stated earlier will be dissociated into oxygen and water. No benefit.
Sodium carbonate will be useful in softening the water. 
Rubbing alcohol (aka isopropyl alcohol, the other IPA)Alcohol is an antiseptic which is commonly used among other things to clean needle sites or cleanse wounds (ouch!). I get that someone might want to take one cleaner (soap) and another cleaner (alcohol) and put them together to make one super cleaner. Better to do a one, two punch: wash with the soap and then spray with the alcohol. This is also the CDC's recommendation for cleaning and disinfecting.
The overall cleaning effect of soap is not affected, at least up to 5% of IPA. Above that concentration, there is a dramatic decrease of foaming, the solution becomes cloudy, and the soap interferes with micelle formation. Although IPA increases slightly the cleaning capability of the soap, it also kills the foaming effect of the Castile soap. It is a fine line. I would recommend not to add more than 5% of alcohol in the blend. This applies to all alcohol containing products: vodka, cognac, Ethanol, IPA, …
Sal Suds with Castile Soap
I’m not sure why you would want to do this. Again, it’s the idea that if both are good separately, then together they must be even better. It’s unnecessary, but chemically speaking there are no adverse effects.
Although there is no interaction between the 2 entities, I don't see any beneficial effect. For sure Sal Suds is more aggressive on the skin.
Salt
Chemically speaking "salt" is a category, not a specific substance. However, most people are thinking of "sodium chloride" which is common table salt, and the base of Sea Salt. Castile soap does not react with sodium chloride, and mixing the two together can make a great exfoliating scrub. Since salt is coarser than sugar, do not use this on sensitive skin. Great for elbows and feet, though. As a category, "salt" is the result of reacting an acid and a base. Soap itself is another kind of salt, as is Epsom salt (see above for reaction).Salt increases the viscosity of the Castile soap to a certain extent.
Sugar
Sugar is a natural humectant, which means that it draws moisture into our skin. This is why we use it in our Organic Sugar Soaps. You can make a lovely scrub by mixing it with Castile soap.
Vinegar
Here’s a whole post I wrote about this one way back in 2011. Vinegar and Castile soap are great separately and terrible together. They’re like the siblings who just can’t leave each other alone. They get all in each other’s business. Vinegar un-saponifies soap. It’s not dangerous, just messy, and ruins the cleaning ability of either. The one caveat is if the soap is buffered by something like baking soda, as in this GIY Soft Scrub recipe.
Vitamin E (tocopherols)
Mixed tocopherols – aka vitamin E – is perfectly fine to mix with Castile. These are the antioxidants we use in our soaps. For personal care, vitamin E is usually recommended for anti-aging properties. For house care, mixed tocopherols is an antioxidant in GIY solutions. Either way, it’s fine to mix with the Castiles to make a solution last longer.
Vodka
The first time a friend told me she used vodka to clean her house, I thought that would definitely make housework more fun. However, she put in a spray bottle, not in a glass. There is some wisdom in this because any alcohol is an antiseptic. As far as mixing it with Castile, see the above section on alcohol. I can think of better uses for vodka.
I did not specifically mix soap with vodka, since this is not a common material that I carry in the lab. (See discussion on alcohol)
Washing soda
Washing soda, or sodium carbonate, is similar to its culinary cousin Baking Soda, or sodium bicarbonate. This is a common ingredient in homemade laundry detergents. Washing soda acts as a water softener as well as a powerful scouring agent. If you are cleaning heavily soiled laundry like towels or work clothes, this will help you a lot. However, it can be a bit harsh, so I do not recommend using much on regular loads, and definitely not on delicates. It combines just fine with Castile soap.
What about a recipe calling for baking soda AND washing soda AND borax? Well, yes, this will scrub your clothes excellently but I hope you like to go shopping because this will wear down your clothes exceptionally fast.
There is benefit to adding sodium carbonate when you have hard water. In this case sodium carbonate precipitates calcium carbonate thus improving the soap’s cleaning capabilities.

124 thoughts on “What Can You Mix with Castile Soap?

  1. can I use Castile soap and ethyl alcohol to create a scented disinfectant for viruses?

    • Hi Donna- The CDC recommends a two-step process for disinfection: wash with a cleaner such as the Castile soap, and then spray with a disinfectant such as alcohol. Combining the two will not work as the alcohol impacts the soap itself. You can add a couple drops of essential oil to the alcohol if you want to scent it.

  2. I’m looking for a thickening agent to add to my Hippie Juice ( a blend that includes Dr. Bronners Castile soap base and essential oils so far ). I’m trying to create a safe for “curly girls” shampoo and conditioner. Please help, I’m not a chemist nor do I have a degree in science but I am a licensed cosmetologist and I want to offer something better for my clients of ALL curl types and straight hair too.

    • Hi Autumn – The only way to thicken the soaps is to use a foaming pump dispenser. Oddly, you’re thickening the solution by adding air. Start with a ratio of 1:3, soap to water, and adjust it to your preference. It’s great to hear you’ve incorporated the soap into your line of work! I need to add, though, that for liability reasons, we don’t authorize selling reformulations that include our products.

  3. Hi Dr Bronner,
    So happy to come accross your blog. I appreciate the useful information knowledge you have here. 🙂
    Just curious if you can dilute castile soap with coconut water or is it best to use regular water that is distilled??
    Also, if you can add aloe vera leaf juice as a mixture to the soap.
    A lastly if you can mix emulsifying wax with castile soaps in the event you are trying to mix certain oils, or honey that seperate from water??

    • Hi Breanna – I’m so glad you’re finding this useful! I haven’t tried mixing the soap with coconut water, but it looks like coconut water has an acidic pH of around 4.8-5.7. Because soap is alkaline, the two would likely react with each other. I don’t think you should mix those two. Aloe vera is at the top of the chart in the artilce – there’s no benefit to mixing it with the soap. Better to apply it afterwards. There are too many types of emulsifying wax for me to give an overall answer. Some already contain a detergent, so mixing them with soap would be a duplication. Both essential oils and honey can be added to the water. Honey will dissolve but the essential oils would need to be shaken to disperse before each use. It sounds like you’re busy making all sorts of interesting mixtures! Good luck with them! We encourage people to use the soap for their own personal combinations, but unfortunately do not permit reformulations that include our products to be sold.

  4. Hello, I want to use Dr Bronner’s unscented soap as my green soap for tattooing. The typical green soap used for tattooing contains 30% alcohol. That soap is then diluted with distilled water to either a 1:8 or 1:10 ratio – there are little to no bubbles at those ratios but it maintains a clean & safe surface to tattoo. I read in the blog that using more than 5% alcohol is not recommended – if I use more than 5% how will that effect the efficacy of the soap? And should I use a lower distilled water to soap ratio? I’m basically looking to make a “water free” wound wash. Any insight you could provide would be greatly appreciated! Thank you!

    • Hi Melissa – I apologize for my delay here. I had to dive into some research myself and I have learned a good bit. I’ll need to update my chart in this blog. While alcohol will cut the foaming of the soap and turn it cloudy, it will not affect its ability to clean. I came across a concentration of 39% ethanol in green soap, close to your 30%. That would be like 1/3 c. ethanol to 2/3 c. Castile (I’d use the Unscented Castile). From what I’ve read about green soap, this comes pretty close to what is generally sold. What do you think?

  5. hello, can I dilute/mix liquid castile soap with rice milk and any other essential oils to make a brightening face wash? Thank your if you answer this!

    • Hi Andhita- Keep in mind that the primary purpose of soap is to grab onto grime and oils and wash them away. Adding rice milk will reduce the cleaning ability of the soap because some of the soap molecules will go after the rice milk and oil molecules.

    • Hi Tamell- Vitamin E – aka mixed tocopherols – is perfectly fine to mix with Castile soap. These are the antioxidants we use in our soaps. For personal care, vitamin E is usually recommended for anti-aging properties. For house care, mixed tocopherols is an antioxidant in GIY solutions.

  6. Can i add tumeric powder to liquid castille soap ? Or would tumeric essential oil do the job?

    • Hi Asha- The ground tumeric wouldn’t react with the soap, but it wouldn’t dissolve either. Instead it would settle to the bottom, so give it a shake before using. Alternatively, you can add tumeric essential oils. You may find this floats to the top, in which case, give it a shake.

  7. Hi Lisa,

    I’m making bath salts w/ essential oils and would like to use castille soap as the carrier. I goofed and used epsom salts only to quickly learn that wasn’t a good idea! Can you recommend a salt that is compatible with castille soap? Thanks!

    • Hi Melinda- Sea salts would be a great option for this. Sounds relaxing!

  8. Hello,

    I would like to mix Castile Soap with Bentonite Clay for a facial cleanser. Do you know if the soap would deactivate the properties of the clay? Or any insight to any other reactions?

    • Hi Paige- This is not something I have done, but in examining the properties of bentonite clay, it has a high concentration of calcium and magnesium. Soap tends to react with these two minerals, swapping out their own sodium and potassium. So I think you might be right that soap might decrease the benefits of the clay. Perhaps use them separately – a clay masque followed by a soap wash, or vice versa.

  9. Hey Lisa I was thinking about adding the organic sugar soap to my African black soap to make it more moisturizing. Is it anything that I need to know or is it a go??

    • Hi Virginia- Without knowing the specific ingredients of the African black soap you have, I can’t comment 100%, but knowing in general what’s in African black soap, it should be fine.

  10. Hi Lisa, came across this concoction and was wondering if adding castile soap would be beneficial? Thanks.

    “TOMATOES along with potatoes, capsicum and chilli peppers, aubergines, tamarillo and cape gooseberries are members of the ‘nightshade’ family. Their foliage contains toxic compounds called alkaloids. These alkaloids are handy for controlling aphids when applied in the form of a spray made from soaked leaves. Not only does tomato leaf spray kill aphids it is also said to attract beneficial predatory insects that ‘home in’ on the smell of tomato and potato plants as they look for prey.
    Ingredients:
    2 cups of chopped tomato leaves
    2 cups of water
    strainer, muslin or coffee filter to strain solution
    spray bottle

    How to make:
    Soak 2 cups of chopped tomato leaves in 2 cups of water overnight.
    Strain liquid the next day (discard leaves).
    Add 2 more cups of water to the solution
    Fill spray bottle. ”
    (https://www.podgardening.co.nz/tomato-leaf-spray.html)

    • Hi Alo- That is a very interesting idea! I have noticed that my tomatoes are always my last plants standing when I’ve had an invasion of pests – be it bug or snails. I really don’t know what the reaction would be between the tomato essence and the soap. If what’s coming from the tomato leaves is an oil, than the castile soap might just bind to that and prevent it from doing its good work. Maybe make this solution and alternate it with insecticidal soap (https://www.lisabronner.com/spraying-for-garden-pests/) to spray on the plants. Let me know how it goes!

  11. Hello, I’d like to mix my unscented liquid Castile soap with jojoba oil and Manuka Honey. I see that you recommend adding no more than ¼ – ½ tsp of jojoba oil per 1 cup of soap. What about honey? How much honey can be added to provide benefits and not decrease properties of the soap? Thank you!

    • Hi Jasmine- Honey is mostly sugar. As is the case with our Sugar Soaps, sugar and soap coexist just fine. I don’t know a recipe or amount to recommend specifically here though.

  12. Lisa,

    I love your articles!

    I have two questions:

    1. Do you have any DIY recipes using Castile soap for laundry and hand washing dishes (to include a separate one for the dishwasher)?

    2. With regards to dishwashing recipes – noted already in question #1: Can add Lemon essential oil, instead of Lemon juice, to breakdown and clean grease and any remaining scum from dishes?
    – Lemon juice does a good job of cleaning grease and scum from dishes however, as you already noted it does not go well with Castile soap.

    Thanks for any recommendations you have!

    • Hi Jeffrey- Thanks for reading! For laundry, use 1/2 cup Castile soap per load, with 1 cup vinegar in the rinse cycle. (Halve for HE machines.) Use a small squirt of Castile soap for hand-washing dishes. More for greasy pots and pans. Or, pre-dilute 1:10 in a squirt bottle. You can add lemon essential oil for scent, but it won’t increase the efficacy. Because our soaps are so bubbly, we don’t recommend them in the dishwasher. My cheat sheet has lots of other uses for Castile soap: https://www.lisabronner.com/dilutions-cheat-sheet-for-dr-bronners-castile-soap/

  13. Hello, I like your article a lot. But could you explain to me what will happen if I combine washing soda, Na2CO3 with water and castile soap/soap on olive base? because if you dissolve na2co3, you get NaOH, (i believe) which is also used to make soap. So do you not make the soap stronger or increase the pH of the existing soap if you put these 2 together? I tried to make my own dish wash soap, but first it was really solid but after a few days, it turned white and thicked. it also hurted my hands because the pH was really high. So i try to understand what had happened. i heated the soap with water and added the soda. I am not really strong with chemistry. Thanks in advance for answering my question, greetings from bianca

    • Hi Bianca – When washing soda dissolves in water, the molecule does not react with the water nor the soap. Chemically speaking, the combo of washing soda, castile soap and water is stable and non-reactive. However, as you noted, washing soda has a fairly high pH around 11. That is pretty harsh on your hands, and it makes sense that your hands would hurt after using this. Though natural, washing soda is a fairly intense cleaner. It is primarily recommended for laundry, although I think it’s too harsh for regular use there. It’s other recommended uses are more for deep cleaning. For regular dishwashing, it’s a bit much. As you’ve noticed, it’s wrecking havoc on your hands. If you do want to add something to the Castile soap for scrubbing extra dirty pots, use a sprinkle of baking soda. You don’t need to pre-mix it. Just sprinkle a bit on the pots as needed.

  14. Hello! What about Percarbonate? And I would love this list but with Sal Suds

    • Hi Valentina- Functionally, Percarbonate is OxyClean, which you can refer to on the list. I’ll have a “What Can You Mix…” post about Sal Suds later this year. Keep an eye out for it!

  15. I’m trying to balance the pH level for a castile soap shampoo (castile soap diluted) and make the mixture more acidic. Will Aloe Vera and citric acid/juice mixed with the castile soap and water do the trick? I do not want to damage my hair by using alkaline and then stripping it down to an acidic solution with a rinse afterwards. Kind of looking for a two in one, I guess.

    • Hi Rebecca- It is not possible to bring the pH of the Castile Soap down, because the soap will unsaponify. The Environmental Working Group’s Skin Deep database ranks products by ingredients, environmental impact and such and would be a good resource for looking for something that meets your needs.

    • Hi Maria- When you dilute the soap, you also dilute the preservative (Vitamin E in the case of our liquid Castile soap), which does shorten the shelf life. It’s best to mix up only what you would use up in a couple of weeks. Storing a coconut oil and soap mixture in the fridge, will cause it to turn solid.

  16. Has anyone asked if you can add activated charcoal to make a detoxifying / cleansing shampoo?

    • Hi Kirsten- I have not done this. If any readers have, please feel free to chime in.

  17. I’m late to this party – but better late than never :D…what about manuka honey? Could that be safely added to castile soap? Thanks!

  18. Hi Dr. Bronner,
    I added Neem oil to Castile soap in my Ortho Dial-N-Spray container, and the mixture turned into a gelatinous mess with the consistency and appearance of caulk. Ruined my Dial-N-Spray plus I lost about $25 of oil and soap. I was trying to kill bugs on my lemon tree.

    It was not until I read down through the comments on this page that I realized a lot of people had similar problems when they mixed in various oils. I think your instructions need to be more up front and tell people to exercise a lot of caution if they try to mix in oils, rather than tell them that oils are ok.

    https://www.lisabronner.com/what-can-you-mix-with-castile-soap/

    • Hi MJ- I’m really sorry that happened to you! Pure neem oil with a neutral pH shouldn’t have this reaction with our Castile soap. I’m following up with our chemist on this one. In the meantime, was the neem oil you used pure, raw oil or was it blended into something?

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