6 Times You Should't Use Castile Soap

Prevent damage and clean the right way by avoiding these common blunders.

December 20, 2016
castile soap

Castile soap is one of the best examples of "simple is better." The versatile soap is traditionally made from nourishing oils like coconut or olive oil, and today’s varieties pass the Environmental Working Group's tests with flying colors.

You can use castile soap to clean just about anything that can be washed with water—but it's only effective if you use it the right way. Stop making these mistakes to get the most out of the iconic cleaner and prevent damage. 

(Still need a holiday gift? Find seasonal recipes, inspiring imagery, and gardening tips every day inside the Rodale’s Organic Life 2017 Calendar!)

punching water
Washing with hard water

Castile soap is an all-magical cleaner—until you mix it with hard water. Then, the minerals in the water react with the soap and cause it to biodegrade. While this isn’t dangerous, it can leave behind a white film on a shiny surface. You don’t have to give up on castile soap completely if you have hard water—it still works great as a body wash and shampoo.

You can also use distilled or softened water for shiny surfaces like counters, glass, and tiles. To make an all-purpose spray, mix a quarter cup of castile soap and a quart of softened or distilled water in a spray bottle. For larger jobs like your car or a sink full of dishes, it’s best to use an environmentally friendly, non-toxic detergent like Dr. Bronner’s Sal Suds or Ecover’s dish soap to prevent film. 

Related: When Did Soap Get So Complicated?

vinegar bottle
iidea studio/shutterstock
Combining with vinegar

Vinegar is a great non-toxic cleaner, but that doesn’t mean you should use it with everything. (Here are 5 times you should never use vinegar around your home.) Combining the soap with vinegar is the most common mistake people make, says Lisa Bronner, public relations specialist at Dr. Bronner’s and granddaughter of the company's founder, Emanuel Bronner. “They are both excellent products to clean your house with, but you get a reaction when you combine vinegar with castile soap that you probably don’t want.”

When added to pure castile soap, or even a mixture that contains small amounts of castile soap, vinegar rapidly reacts with the soap and breaks it back down to its original oils. Not only does this mean you’ve turned your soap into a curdled, oily mess, but your vinegar isn’t going to be doing any cleaning either. If you’ve ever tried to combine castile soap and vinegar in a spray bottle, you've probably seen the hazy white hue or lumps that form—those are solidified oils.

If you really want to clean with both vinegar and castile soap, use them one at a time, with a good rinse in between.

wind blown hair
iiii iiii/pexels
It's your shampoo—and you have dyed hair

While castile soap makes an excellent shampoo alternative, it might strip the dye from colored hair. Castile soap is alkaline, which means it opens up the cuticle of the hair and exposes the inner fibers where the dye is stored. Color-safe shampoo is typically slightly acidic to prevent this from happening. However, the effect of the castile soap seems to depend on the dye. Some dyes, especially those made with henna, may not be affected according to Bronner. No matter what, it’s always best to test a small, inconspicuous section of dyed hair before using to make sure that your castile soap or shampoo doesn’t remove the color. 

cleaning supplies
Sergey Mironov/shutterstock
Mixing with other household cleaners

Much like vinegar, you don’t want to combine castile soap with any other household cleaners like bleach or ammonia. Bleach reacts with the soap to form a caustic salt that can burn your skin and potentially damage what you're trying to clean. It’s best to avoid mixing castile soap with any premixed cleaner like a tile spray because there’s no way of knowing what’s in the cleaner. Companies do not have to list the ingredients in their cleaning products.

However, simple household ingredients like salt and baking soda are great, safe additions to the cleaning power of castile soap. You can also safely add essential oils and tea tree oil to the soap.

Related: 7 Mistakes You're Making When You Use Green Cleaners

measuring spoon
Not properly diluting it

Don’t be fooled by its thin consistency—castile soap is highly concentrated. You don’t need much at all for the job at hand. Not properly diluting castile soap won’t damage your surface or hurt your skin, but it is a waste of soap (and water). You only need 2-3 drops to wash your face or hands, less than a tablespoon to wash your hair, and a teaspoon or two can easily clean a whole tub. When in doubt, start with less. You can always add more.

tooth paste
sercan samancii/shutterstock
Using it as your toothpaste

Yes, you can brush your teeth with castile soap—just ask the hardcore-backpacker in your life. But it will taste and feel like soap. Unless you’ve been particularly foul-mouthed lately, maybe skip the castile soap on your toothbrush. You can make your own toothpaste instead.