Don’t Fall for These 8 Common Castile Soap Cleaning Mistakes

Like the swiss-army knife of cleaning, castile soap has more household and personal care uses than we can count. (It makes a great DIY laundry soap, natural bathroom cleaner, and bubble bath, just to start.) Castile soap is (among about a million other things) cheap, versatile, and biodegradable — which means it’s safe and easy to use on many surfaces, fabrics, and even your body.

But keep in mind that just because something is “natural” doesn’t mean it’s effective (or safe) to use on everything under the sun. Curious how to put that bottle of Dr. Bronner’s to use in your home? Start with how not to use it.

Remember learning about acids and bases in high school science? While acids (like vinegar) and bases (like castile soap) are powerful cleaning tools on their own, Lisa Bronner — Dr. Bronner’s granddaughter — cautions mixing Castile with any acidic ingredients.

Rather than doing double-duty cleaning a given surface, a mixture of castile soap and vinegar or lemon will accomplish the opposite, resulting in a white, curdled solution that will likely leave a yucky film behind on your counter.

Back to acids. Castile soap is a reliable and thorough cleaner, but on shiny or hard surfaces, it can leave a deposit of salt film behind. Even though you want to avoid mixing castile soap with acids, vinegar or lemon are great tools for cutting the leftover salt deposit. For Castile-washed dishes, Lisa Bronner recommends dipping them in a vinegar-water solution of 1 cup vinegar per quart of water. You could use a similar solution to rinse filmy countertops.

Given its high mineral content, using castile soap (remember the salt deposits?) with hard water can result in some extra soap scum or residue. While your surfaces are probably still clean, mixing hard water and castile soap means you’ll probably have to use the vinegar solution every time.

If you’re into the “no poo” method, castile soap is a great option for a squeaky-clean scalp — try pre-mixing a tablespoon of liquid Castile with a cup of water. But, as Dr. Bronner’s website notes, the soap can also leave your hair tangled and matted. The best solution for silky, soft hair? Dr. Bronner recommends following up with an acidic conditioning rinse, like apple cider vinegar or their lemon juice formula.

Like baking soda, castile soap — even though it’s chemical-free — can be harsh on dyed or highlighted hair, stripping follicles of color. To protect your colored hair, it’s probably best to stick with a color-safe shampoo.

Castile soap can be a powerful insecticide, but it’s important not to overdo it on your plants. Since it can remove a plant’s natural protective, waxy coating, spraying too much castile soap directly on your plants could leave them more susceptible to pathogens or even burn them. If you find your plants are damaged after spraying with your DIY insecticide, cut the castile soap in your solution in half.

One of the best parts about castile soap is how long it lasts — it’s a concentrated product, so you can use a bottle of it for a pretty long time, without the guilt of too much single-use plastic waste. But that doesn’t mean you should buy five bottles to keep on hand. As with any other cleaning product, it’s important to remember that castile soap has a shelf life of about three years. Your bottle should have an expiration date, and it’s always a good idea to follow it. 

Again, castile soap is meant to be diluted, so it’s not usually a good idea to apply it directly to a surface without watering it down or mixing it with something else. In general, the more castile soap you use, the more pesky film you’ll end up with on whatever you’re trying to clean (especially if you have hard water). To prevent that annoying residue, you can always add baking soda to your cleaning mixture or, if the damage is done, whip out the vinegar. It’ll quickly break up the film. Just don’t forget not to mix anything acidic with the soap.