The Truth About pH in Handmade Soap: Why “Too Alkaline” Is the Wrong Question

The pH “problem” that won’t die

If you’ve spent five minutes in soapmaking forums, you’ve probably seen this one:

“I want to make a face bar, but I was told that handmade soap’s pH is too high, so you can’t use it on your face (or hair).”

Here’s my take, as someone who loves both soap chemistry and practical real-world bars (and washes her face and hair with real soap): handmade soap is alkaline because it’s soap. That’s not a defect, it’s the definition.

Also: pH alone is a terrible shortcut for deciding whether a soap will feel gentle, drying, lovely, or “oh no, why is my face tight?” The bigger story is formulation, superfat, cleansing power, rinsability, additives, and your own skin and hair.

Let’s bust the most common pH myths—without pretending pH is meaningless.

Soap pH Myth Busting:

First: what pH tells you (and what it doesn’t)

True soap (saponified fats + sodium hydroxide or potassium hydroxide) creates alkali salts of fatty acids—that’s literally what “soap” is in chemistry terms (and per the FDA for those selling soaps in the US)

Because soap salts interact with water in a way that creates an alkaline solution, soap solutions are naturally alkaline. So yes—handmade bar soap usually lands somewhere around ~8–10 when tested as a diluted solution, and that’s normal.

What pH doesn’t tell you by itself:

• whether the bar is “safe”
• whether it’s lye-heavy (caustic)
• whether it will feel drying or gentle on your skin
• whether it will work well as a shampoo bar for your hair

Soapers don’t just get confused about what pH is—we also get confused about how to accurately test it. If you’ve ever tried pH strips on a bar and ended up with a rainbow of “wait… what does this mean?” I’ve got you. This guide walks through the best ways to test soap pH, and it also includes a real laugh-out-loud video of me explaining the zap test: How to pH test your soap (and zap test).

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Myth #1: “If soap isn’t pH 5.5, it’s automatically bad for skin”

Skin’s surface is slightly acidic (often discussed around ~pH 5-ish), which is why you’ll hear about the “acid mantle.” But here’s what gets skipped in a lot of internet arguments: cleansing can raise skin pH temporarily, and then skin tends to drift back toward its baseline.

Where the caution belongs: if someone has very dry skin, eczema, or a compromised barrier, higher-pH cleansing can aggravate symptoms and feel worse—this is one reason some dermatology guidance leans toward syndets or non-soap, non-detergent alternatives for those folks.

Bottom line: pH matters, but it’s not a universal “soap is forbidden” rule.

Myth #2: “You can’t use handmade soap on your face because the pH is too high”

Face skin is not magical unicorn skin. It’s skin. What usually makes a facial bar feel “too harsh” isn’t that the pH is 9-ish instead of 5-ish. It’s more often that the bar is:

• too cleansing for that person’s skin (fatty acid profile matters),
• too low in free oils (superfat matters),
• used too often or with hot water (routine matters),
• or simply not a good match for their climate and skin type.

Some people do prefer syndet bars—and for some skin types they’re a better fit. But they’re not the only alternative. For very sensitive or reactive skin, non-soap options like water-only cleansing, oil cleansing, or other gentle cleansing methods can be a better match than either true soap or syndet.

So I’m not here to say “soap always wins” or “syndet always wins.” I’m here to say: match the cleansing method to the skin.

Myth #3: “If a soap is drying, that proves the pH is wrong”

Drying and irritation are multi-factor problems. If someone says, “This bar makes me feel tight,” the fix is usually:

• tweak the cleansing vs. conditioning balance (fatty acid profile),
• adjust superfat,
• improve rinsability (hello, hard water),
• adjust usage (less often, cooler water, moisturize after)…

…not “make the pH 7” (because you can’t do that and still have true soap).

Myth #4: “The only difference between a dish bar and a body bar is pH”

Nope—and this is where soapmaking gets fun.

A dish/laundry-style bar is typically formulated to be:

• highly cleansing,
• low superfat (often 0–1%),
• designed for maximum residue-free cleaning.

A body bar might use similar base oils but with a higher superfat and/or a different fatty acid profile so it feels less stripping. That’s why I always come back to this: soap is soap, but soap performance is absolutely tunable.

One important safety note, though: people sometimes talk casually about “negative superfat” (lye excess). That can be appropriate in some industrial contexts, but for handmade body soap, I don’t recommend intentionally lye-heavy bars—it raises the risk of a caustic product if anything is off in weighing, calculation, or mixing.

Myth #5: “Shampoo bars fail because soap pH is too high”

This is where the pH argument gets the loudest—and the reality is more nuanced.

True soap shampoo bars can and do work for a lot of people, and they can also be frustrating for others. The common culprits are usually:

• Hard water + buildup
• Hair feel preferences (some people want that ultra-slippy conditioned feel that syndets deliver)
• Technique (not fully wetting hair, not rinsing thoroughly, washing too often, etc.)

Also, when you see people cite “shampoo bars” with a lower pH (often around the 5–7 range), those are typically syndet bars, not true soap. My Shampoo Bar class is specifically about true soap shampoo bars (oils saponified with NaOH), and I go into the real-world tradeoffs, troubleshooting, and how to decide if soap shampoo is a good fit for your hair.

If you want the full deep-dive (including formulations, rinses, technique, and what to tweak in formulation), my Shampoo Bar class is here.

Alternative cleansing options for sensitive skin

If your skin is reactive, sensitized, barrier-compromised, or eczema-prone, you’re not “failing” at skincare if soap (or syndet) isn’t your best match. A few alternatives that can work beautifully:

• Water-only cleansing
  Especially in the morning, or when you’re not removing heavy makeup/sunscreen. Sometimes “less product” is the win.
• Oil cleansing (oil washing)
  Can be gentler for some people because it relies more on dissolving oils and grime than on strong surfactants. Works best with a soft cloth and a thorough rinse.
• Very gentle non-soap cleansers
  This could include cleansing creams, milky cleansers, or other low-irritant formulas. (The key isn’t the category—it’s how your skin responds.)
• Short-contact cleansing
  Whatever you use, keep it brief: apply, cleanse, rinse—no long “masking” with cleanser.

No matter the method: the best cleanser is the one your skin tolerates consistently.

Why syndet bars can still irritate some sensitive skin

Even though syndet bars are often discussed as “gentler,” they can still be irritating for some folks, because irritation isn’t only about pH. Common reasons include:

• Surfactant sensitivity (some skin reacts to certain detergent systems)
• Fragrance and essential oils (a huge culprit, even in “gentle” products)
• Preservatives, dyes, and other additives
• Over-cleansing (frequency and water temperature can wreck a routine)

So if someone tries a syndet and says, “Nope, still irritated,” that’s not a contradiction. It just means their skin needs a different approach.

Practical takeaways you can share with other soapmakers (for the anti-confusion bandwagon!)

• Yes, handmade soap is alkaline. That’s normal—soap is soap.
• A higher pH number doesn’t automatically mean a product is “too harsh.”
• Whether a bar feels gentle is mostly about formulation, superfat, cleansing strength, rinsability, and your routine—not the pH alone.
• If someone has eczema or very sensitive skin, they may do better with an alternative cleansing method such as a syndet bar, water-only cleansing, or oil washing.
• Shampoo bars: many lower-pH “shampoo bars” are syndets; true soap shampoo bars are a different tool and need different expectations and troubleshooting.

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Want help making a bar that actually feels right (without chasing pH myths)?

Inside Soapy Friends, I teach the things that genuinely change how soap behaves on skin and hair—superfat strategy, fatty acid profiles, cleansing balance, and how to test and tweak your formulas with confidence.

If you’ve ever thought, “Why does this bar feel drying?” or “How do I make a face bar that works for my skin?” you’ll feel right at home.

→ Explore Soapy Friends membership
Or start with my Shampoo Bar class (true soap, not syndet).

No pressure—this post is yours to use and share. If you want deeper support, I’d love to have you.