Dr. Bronner's Products

Sal Suds or Castile Soap – Which to Use?

I talk a lot about the exceeding versatility of Dr. Bronner’s Castile Soap and Dr. Bronner’s Sal Suds. There are so many overlapping uses. But is there any time in which they aren’t interchangeable? Yes, but just a few.

Castile soap is primarily designed for the body. The blend of oils (coconut, olive, palm, jojoba, and hemp seed) are designed to be the most nourishing to our skin. But wait, there’s more. Because it is such a beautifully simple soap, it also cleans many other things amazingly well, whether it’s your dog, your sinks, or your floors. You can find details of all these uses on this Castile Soap Dilutions Cheat Sheet.

Because Castile soap is a true soap, it reacts with the minerals contained in hard water. (Here’s my test to find out if you have hard water.) The more dissolved minerals there are, the “harder” the water. The reaction of soap with these minerals in the water leaves behind an insoluble film that’s commonly called “soap scum”. This term is a bit of a misnomer, because it’s not actually soap that remains, but a precipitate of minerals.

You’ll only notice this on shiny objects that are left to air dry. They will take on a whitish film. (Read my post on eliminating soap scum.) Also, absorbent fabrics like towels and cloth diapers will become stiff and lose their absorbency. (But laundry in hard water is still doable – Read more here.)

Enter Sal Suds. This is our biodegradable household cleaner developed by my dad. Sal Suds doesn’t react with hard water. It rinses cleanly and leave surfaces sparkling. No more film on the tub or towels! For it’s multitude of uses, see the Sal Suds Dilution Cheat Sheet.

That’s all well and good, but I haven’t answered that initial question of what to use when.

Situations where I exclusively use Castile Soap

  • Myself – Head to toe.
  • My animals – Any Castile soap scent on my dog. Baby Unscented on my cat.
  • Pest Control – Only Castile soap has this ability to eliminate insects.

Situations where I exclusively use Sal Suds:

Other than these few cases, I reach for whichever is closer at hand.

Now you know what to use, but perhaps you want to know why?

Soap and detergent are both surfactants. The word “surfactant” is a portmanteau of “Surface Active Agent.” If you’ve ever done a belly flop into a pool, then you’ve felt the power of surface tension. Surfactants break through the surface tension of water and make water really soak in.

My brother Mike says: Surfactants make water wetter.

The second magical power of surfactants is that they make oil and water coexist. Which they don’t otherwise like to do. This is why you can’t just rinse oil off your hands. The water runs over the oil like it’s just not there. And it just doesn’t care.

Now brace yourselves – you’re about to learn some Greek!

Surfactants solve the oil/water repulsion because one end of each surfactant molecule is hydrophilic and the other end is hydrophobic.

Hydrophilic literally means “water (hydro) loving (philic).” This end of the surfactant molecule grabs hold of water. On the other side, hydrophobic means “water (hydro) fearing (phobic).” A little exaggerated perhaps, but this end grabs the oil.

But we’re not talking about just one. Surfactant molecules work in groups. In a solution, they float around looking for oil molecules and snag with those hydrophobic tails, totally surrounding each oil molecule so there’s no part of the oil molecule left exposed to water. This little nugget is called a micelle.

The outside of this micelle is now entirely hydrophilic, which means instant attraction to the passing rinse water which carries it all away.

It’s like they’re filling those oil molecules with a whole lotta love and reaching out and connecting them with their former enemy, those water molecules. And once they’re connected, they realize it’s not so bad. They can get along. They can hang out together. I think there’s a larger lesson here.

You still with me?

So they’re both surfactants. Now for some differences.

Soap is close to nature, made by a beautifully efficient one-step reaction of combining oil (coconut, palm, olive, jojoba, and hemp for our Castile) with a strong alkali such as sodium or potassium hydroxide (the first also known as lye). Out of this combo, you get soap, glycerin and water. Bam! No leftovers. No waste. Beautiful.

Detergents are more complex and must be synthesized. They were developed during the World Wars when the oils needed for soap were scarce. They can start with botanical substances (such as coconut oil for our Sal Suds) or with petroleum derivatives. And the uses of detergents is vast and wide.

Tidy as it would be, I can’t sum it all up by saying, “Soap good. Detergent bad.” That would be a gross oversimplification. There are bad soaps (not ours, of course) that are poorly made with bits of unreacted alkali floating around in them ready to saponify your very body. You become walking bar of soap. Ouch!

And there are excellent detergents, such as our Sal Suds, which is super duper tough on grease and completely clean rinsing, yet mild and biodegradable.

So that’s a little bit more about the magic of cleaning and the beauty of chemistry.

Download Now!

Castile Soap Cheat Sheet

Dilute! Dilute! OK! But how much? Print this guide!


Download Now!

Sal Suds Cheat Sheet

Sal Suds, Sal Suds, How do I love thee?


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Nik says:

Hi can you please Inform me as to why all Uk stockist even Amazon are sold out of Sal suds? I can’t even purchase and import it!

Lisa Bronner says:

Hi Nik- Unfortunately, due to regulatory requirements we are not actively selling Sal Suds in the UK. At the moment we do not have a timeline for when we will be reintroducing Sal Suds to the market. I’m sorry for any inconvenience this has caused. In the meantime, our Castile Liquid Soap can be used for household cleaning purposes. Check out my dilutions Cheat Sheet for dilutions and recipes:

Isabelle says:

Hi Lisa! I made a dishwashing detergent with Sal Suds but it is too liquid for my liking, so I thickened it with guar gum. However, that made the cleaning solution lose all its sudsing power. Did it lose its cleaning power as well, or just the suds? And how can I turn the cleaning solution into a gel without losing the suds? I’m not a good chemist, apparently 🙂

Lisa Bronner says:

Hi Isabelle- I’m not familiar with the impact of mixing Sal Suds and guar gum. Sorry not to be of more help.

Clean Like a Pro with Organic Ingredients – Regina Ryerson says:

[…] used Seventh Generation, though most brands work the same. For worst-case grease, go straight to Dr. Bronner’s Sal Suds. Either works better than castile soap in hard water […]

Anna says:

Can you advise what dilution & which type of Dr.Bronner’s should I use to clean gardening pots especially those that have been infested/housed with garden pests/bugs.

Lisa Bronner says:

Hi Anna- I’d use Sal Suds because it doesn’t react with the minerals in hard water the same way Castile Soap does. Hose off the pots first to remove loose debris and soil. Add a small squirt of Sal Suds to a large bucket of water, and in the case of hearty terracotta pot, a brush to clean. For anything painted or decorative, a soft brush or a cloth is a gentler option.

Richard says:

Hi Lisa, I always learn so much from your articles. There is now some research recommending adding a little baby shampoo to sinus rinse as a surfactant (google Baylor medicine sinus rinse baby shampoo). Any thoughts on Castile Soap vs Sal Suds in this instance? Thanks!

Lisa Bronner says:

Hi Richard- It’s great to hear my blog is a helpful resource to you! I would request that you run this idea by a medical professional. We ourselves do not advise using the soap internally. Our nasal passages are very sensitive to any foreign matter, and soap or detergent can irritate sensitive tissues, especially if it is not fully rinsed out.

Holly says:

Hi Lisa I live in the U.K. and am a bit distressed to discover that Sal Suds has been discontinued here! What is going on?! I need it back in my life!

Lisa Bronner says:

Hi Holly- I’m sorry to report that Sal Suds is undergoing a label update due to Brexit requirement changes and is unfortunately unavailable in the UK for the next several months. However, we hope to bring Sal Suds back to the UK in the later part of 2022. In the meantime, our Castile Liquid Soap can be used for household cleaning purposes. Check out my dilutions Cheat Sheet for dilutions and recipes:

Erin Pelosi says:

I am going to start using the baby castille as a body wash, can essential oils be added for scent? I always use the soaking tub. Will the soap leave the whitish film?

Would I use the sal suds to clean or the castille with baking soda?

And I usually wash the soaking tub right away with baking soda and baby wash. Then spray it with an alcohol or vinegar homemade cleaner.

I just started making my own cleaners, what ingredient can be added to have it be a disinfectant?

Thank you!

Lisa Bronner says:

Hi Erin- Yes, adding essential oils to the Castile Soap is a fun way to customize your scent with the season, your mood, and so on! If you have hard water, it’s likely a white film will build up in your tub over time. Soap scum is simply a reaction that occurs between a true soap, like Castile, and minerals naturally occurring in hard water. It’s unsightly, but not harmful, and easily cleaned with diluted vinegar or scouring with baking soda. Check out my post all about soap scum here:

Soaps clean by grabbing onto dirt, germs and grime, and rinsing them off. Here’s my deep dive into how soap works Disinfecting should be reserved for times when there is sickness present, or of course in medical facilities. It’s the idea to use the least intensive strategy necessary for the situation and to reserve the more intense measures for circumstances that merit them. This preserves the effectiveness of the intense measures and avoids their potential negative side effects.

Erin Pelosi says:

Absolutely loved the article!
Was just trying to figure out which soap to get- and I was just thinking about the oil and water dilemma especially with essential oils. Lisa, you gave me alot of knowledge! Thx,

Sunny says:

hello, I am new to Dr. Bronners products.
I have a recipe for homemade cream cleanser using Pure Castile Soaps.
I am wondering if I can use Sal Suds instead.

Lisa Bronner says:

Hi Sunny- Welcome to the Dr. Bronner’s family! If you’re cleanser is for household cleaning, most likely yes. Sal Suds is quite a bit more concentrated than Castile Soap though, so use less. If the cleanser is for skin care, stick with the Castile Soap. While Sal Suds is not harmful on skin, it’s intended to be used as a household cleaner.

Carole says:

Dr. Bronners products are the best! I remember Aunt Gladys used to send us soap for Christmas with a card that said “ your health is your greatest wealth” Its hard to find here in MN, so I’m glad to see it’s available through Grove, so everyone can fall in love with Pure Castile Soaps , even if not carried locally

Lisa Bronner says:

Hi Carole- Thank you, Aunt Gladys! I love hearing stories like yours. Thank you for sharing!

Ann says:

Hi, would the sals suds cleaner be safe to use on wooden flooring with pets? My dog sleeps on the floors a lot and tends to lick them as well.

Lisa Bronner says:

Hi Ann- My 2 dogs and 2 cats can attest to the fact that Sal Suds is gentle and exceedingly clean-rinsing when it comes to cleaning around pets. And, customers who own birds and reptiles tell us Sal Suds is a safe and effective cleaner for cages and enclosures. The concern around pets is essential oils. Our products have a small amount of essential oils, just 2%, which are then highly diluted with water in the All-Purpose Spray and mopping solutions.

Bonnie says:

Should dr. Bronners Castile liquid soap be diluted for showering?

Lisa Bronner says:

Hi Bonnie- The water in the shower does the diluting for you. Use a small squirt in a wet cloth or hands. Use 2-3 drops for face-washing. You’ll find a little goes a long way!

Christine says:

Is it ok to use unscented sugar soap for hand washing dishes? I have recently developed severe skin sensitivities as a side effect form a medication. Between Castile, Sugar Soap and Sal Suds, Sugar Soap leaves my skin feeling the best, I love it!

Lisa Bronner says:

Hi Christine- It’s great to hear the Sugar Soap works well for your skin! While I’ve not tried it on dishes, the Sugar Soap cleans in the same way Castile Soap does, so if its working for you – keep on doing what you’re doing! One note here, the Castile Soap is highly concentrated and requires diluting, while the Sugar Soap is diluted with organic grape juice, so there’s no need to further dilute.

mari says:

Should I use Castile or Sal Suds for cleaning the interior of my refrigerator…shelves, racks, walls?

Lisa Bronner says:

Hi Mari- Both would work beautifully. I typically turn to Sal Suds for this task though. Castile Soap interacts with the minerals in hard water, which I have, and can leave spots on shiny surfaces and glass.

Heather says:

Would love it if Sal Suds came unscented! We have allergies to pine, but love your unscented line!

Lisa Bronner says:

Hi Heather- We always appreciate consumer suggestions! I’ll pass your excellent idea along.

michelle says:

I’m allergic as well. I’d love to see something made without pine or spruce. Or if you can point us in a direction for alternatives. Also, an unscented castile soap without fragranc or hemp. I just found out I’m allergic to hemp as well so I have to abandon Dr. Bronner’s altogether! 🙁

Lisa Bronner says:

Hi Michelle- I’ll add your vote for new Sal Suds scent! The Environmental Working Group ( or your local natural grocer would both be great resources for finding a soap made without hemp seed oil.


Lisa Bronner

Green means life. “Going Green” is living in such a way to promote vitality and vibrancy in every sphere of life. Grab an idea to make your days healthier, simpler, and more beautiful at their core.

Download Now!

Castile Soap Cheat Sheet

Dilute! Dilute! OK! But how much? Print this guide!


Download Now!

Sal Suds Cheat Sheet

Sal Suds, Sal Suds, How do I love thee?