Yes, castile soap can be a good shampoo, with one big catch and a couple of small ones. Plenty of people wash their hair with nothing but a bar of castile and a splash of vinegar and swear they'll never go back. Plenty of others try it once, end up with hair that feels like a doll's, and go straight back to the bottle. The difference usually comes down to three things, the rinse, the water and a little patience.
Is castile soap good for hair?
It cleans hair and scalp very well, which is the job of a shampoo. Castile soap is true soap made from plant oils (traditionally all olive oil, which is how our castile bars are made), and it lifts oil and dirt as well as anything in a bottle.
The catch is that soap is alkaline, and hair likes things a little on the acidic side. Washing with soap can leave the outer layer of each hair, the cuticle, a bit roughed up, like shingles lifted on a roof. That's what makes hair feel tangly, squeaky or straw-like after a soap wash. Even Dr. Bronner's, the best-known castile brand in the country, says this on its own hair-washing guide and gives the same fix we would.
The rinse is the whole trick
After you wash and rinse out the soap, follow with a mild acidic rinse. It smooths the cuticle back down, and that's what takes hair from tangly to soft. The usual recipe is simple.
- Mix a tablespoon or two of apple cider vinegar into a cup of water.
- Pour it over your hair, work it through, and leave it a minute.
- Rinse it out, or don't. The vinegar smell disappears once your hair dries.
Lemon juice in water works too. Keep either one out of your eyes. Some people find their hair feels fine without the rinse at all, but if your first castile wash goes badly, the missing rinse is almost always why.
How to wash your hair with a castile bar
- Wet your hair thoroughly.
- Rub the bar between your hands to work up a lather, or rub it directly along your scalp a few times if your hair is short.
- Massage the lather into your scalp. You don't need much, and the ends get clean as the suds rinse through.
- Rinse really well. Leftover soap is the main cause of a waxy feel.
- Follow with your acidic rinse, then condition the ends if your hair is long or dry.
A pure olive oil bar makes a small, creamy lather rather than big bubbles. That's normal, and it doesn't mean it isn't working.
Hard water changes everything
If you have hard water, minerals in it react with soap and can leave a dull, waxy film behind. This is the single most common reason people give up on soap for their hair. A few things help. Rinse longer than you think you need to. Use the vinegar rinse every time. A shower filter or a jug of distilled water for the final rinse makes a noticeable difference for some people. And if your water is very hard, castile may simply not be the right shampoo for you, which is fine.
Expect an awkward few weeks
Most conventional shampoos and conditioners leave silicones and other coatings on hair, which is what gives it that slippery-smooth feel. When you switch to soap, your hair has to shed all that, and the first two to four weeks can be strange. It may feel greasier than usual, then drier than usual, before it settles. Some people skip the awkward phase entirely. If you're going to try it, try it for a month before you decide.
Troubleshooting
- Tangly or straw-like. Add the acidic rinse, or make it a little stronger.
- Waxy or coated. Rinse longer, use the vinegar rinse every time, and consider your water hardness.
- Greasy. If you're in the first few weeks, give it time. After that, use less conditioner and massage your scalp a little longer while you wash.
- Dry ends. Wash less often, use less soap, and condition the ends. A drop of oil on dry ends after washing helps too.
- Color-treated hair. Ask your stylist before switching. Soap is different from the shampoos they usually recommend.
If your scalp is itchy, flaky or irritated and it doesn't settle down, that's one for a dermatologist rather than a change of soap.
Can you use any bar soap on your hair?
You can, but most bars aren't great for it. Heavily scented bars, bars with scrubby bits, and detergent bars made for skin aren't designed with hair in mind, and some leave a residue. A plain castile bar is about as simple as a bar gets, which is why it's the one people reach for. Our plain Castile Soap is fragrance-free, and the Peppermint & Rosemary is a nice wake-up if you like a little scent in the shower.
So, should you try it?
If you like the idea of one bar for everything, less plastic in the shower and a short ingredient list, it's worth a month. Use the rinse, mind your water, and give your hair time to adjust. If it doesn't work out, you'll still have a very nice bar of soap for the rest of you. And keep it on a dish that drains between washes, because olive oil soap goes soft fast when it sits wet. More on that in how long a bar of soap lasts.