Sodium hydroxide has a reputation that makes many skincare enthusiasts uneasy, and for good reason. 

Image source -> Britannica

In its pure form, it's a caustic, high-pH compound capable of burning skin and eyes. 

But what most people don’t realize is that in soapmaking, sodium hydroxide doesn’t remain as-is. It undergoes a complete chemical transformation called saponification, bonding with oils to create the solid soap you hold in your hand. 

No lye, no soap, it’s that fundamental. 

Still, the presence of sodium hydroxide on an ingredient list raises a few questions:

Can it linger in the final bar? 

Could it still cause dryness or irritation, especially for sensitive skin? 

As someone who oversees product formulation here at Legend’s Creek Farm, I believe consumers deserve clear answers backed by both science and experience. 

Why Is There Lye in My Soap? (And What Is It, Really?)

Sodium hydroxide, also labeled as NaOH, lye, or caustic soda, is a strong alkali compound used in everything from industrial degreasers to hair relaxers. 

In its unreacted state, it’s hazardous: corrosive enough to burn skin, blind eyes, or damage lung tissue if inhaled. That association understandably makes people uneasy when they see it listed on a soap label. 

But in soapmaking, sodium hydroxide serves a completely different purpose, one rooted in chemistry, not cleaning agents.

Soaps can’t exist without saponification. This is the process where sodium hydroxide reacts with fats or oils, breaking apart triglycerides and creating a new substance: soap. 

During this chemical reaction, the sodium hydroxide is fully consumed. In a properly formulated and cured soap, no free lye remains, what’s left are fatty acid salts (the actual soap) and naturally occurring glycerin.

The comparison to drain cleaner stems from misunderstanding, not misuse. 

Yes, sodium hydroxide is in both, but context and concentration are everything. Industrial products use it in high concentrations, often above 50%. 

Skincare formulations, especially cold-process soaps, use it as a reactive agent that’s calculated down to the gram. When used correctly, the final bar contains none of the original compound in its raw, caustic form.

Some ingredient lists still include “sodium hydroxide” due to labeling laws that require disclosure of all inputs, even if they’re chemically altered or no longer present. 

That can confuse shoppers, who assume anything named must still exist in the final product. But there’s a critical difference between an ingredient that’s added and one that remains.

Understanding that distinction is key. 

Lye is dangerous on its own, but in expert hands, it becomes an invisible bridge between oil and cleansing power. The skill lies in the formulation, not the fear. And in a well-crafted bar, that transformation is complete.

Is Sodium Hydroxide in Soap Safe for Skin?

When we talk about whether sodium hydroxide is safe for skin, the answer depends entirely on context, specifically, the concentration used and the quality of the formulation. 

It’s not the presence of sodium hydroxide that determines safety; it’s the chemistry that happens after it’s introduced. In soap, sodium hydroxide is a tool, not an active ingredient in the final product. But like any tool, it can be misused.

Understanding the Real Risks

Concentration is everything. Pure sodium hydroxide is extremely dangerous, it can cause chemical burns, permanent tissue damage, and serious respiratory harm if inhaled. 

However, in soapmaking, it’s used in strictly controlled amounts to initiate saponification. 

Once that reaction is complete and the soap is properly cured, no free lye should remain. What you're using on your skin isn’t sodium hydroxide, it’s the result of a completed chemical transformation.

The FDA permits sodium hydroxide in cosmetics under clear concentration limits, and it’s even used in food processing (like peeling fruits and vegetables). Its safety in trace amounts is well-established, as long as it’s used correctly.

That said, some people do experience skin reactions from soaps made with sodium hydroxide, but lye itself isn’t always to blame. 

Dryness or tightness after washing is often linked to poor formulation, specifically, using too much lye or not enough moisturizing oils. It can also happen when soap is under-cured or lacks superfatting, which leaves the skin stripped of its natural oils.

Reactions like itching, redness, or flaking are more common in individuals with sensitive skin, and they’re often worsened by added fragrance oils or botanicals like clay. 

One user shared, “I used a natural bar soap and my face felt slimy during the wash and tight after. Is this normal?” 

That sensation could come from excess lye, but it’s just as likely caused by the type or ratio of oils used, or how the soap interacts with facial skin, often more sensitive than the body.

Ultimately, irritation is rarely about sodium hydroxide alone. It’s about the balance. 

When a soap is carefully formulated and properly cured, it shouldn’t cause burning, stinging, or dryness. If it does, the issue lies in how it was made, not the ingredient that made it possible.

How Can You Tell If a Soap Is Too Harsh?

Some soaps just don’t feel right on the skin. Maybe your face feels tight after rinsing, or your hands feel dry no matter how much you moisturize. 

These reactions often leave people blaming sodium hydroxide, but more often than not, the culprit is a poorly balanced formula. 

When a soap is made without enough fats to fully neutralize the lye, or not cured long enough, residual alkalinity can linger in the final product, which may trigger skin irritation or barrier disruption.

Signs of Residual Lye or Poor Formulation

There are a few telltale signs that a soap might be too harsh. 

Persistent tightness, especially on facial skin, can suggest a high pH or lack of moisturizing ingredients. 

Redness, flaking, or an itchy sensation after use, especially if you haven’t introduced any other new products, could also point to leftover lye or overly aggressive cleansing agents.

You can test the soap’s pH at home using pH strips (also called litmus paper). Dissolve a small piece of the soap in warm water, then dip the strip into the solution. 

A safe pH range for soap is typically between 7 and 10. If the result is above that, the soap may be too alkaline and more likely to disrupt your skin’s acid mantle. “Can I test my soap’s pH at home to see if it’s safe?” 

Absolutely, and it’s a smart way to confirm what your skin might already be telling you.

One common misconception is that a slippery or “slimy” feel during washing indicates poor quality or leftover lye. 

In reality, that sensation is often caused by a high concentration of moisturizing oils like olive or avocado oil. These fats can leave a silky layer behind, especially in super-fatted soaps, and usually signal richness, not danger.

When in doubt, pay attention to your skin’s response. A well-made bar should cleanse, not strip.

Sensitive Skin? What to Look For in a Safe Soap

There’s no such thing as a lye-free soap. 

Every true soap, whether handmade or commercial, starts with sodium hydroxide. But here’s what matters: in a well-made bar, the lye doesn’t stick around. 

Once it’s reacted with oils in a process called saponification, it’s chemically transformed. What you’re left with is soap, not residual sodium hydroxide. So the better question isn’t, “Is there lye?” but “Was the soap made well enough that none of it remains?”

One sign of a skin-friendly soap is superfatting, where extra oils are added beyond what’s needed for full saponification. 

These leftover oils don’t just improve the feel, they actively nourish skin and form a protective barrier to reduce dryness or irritation. Superfatted soaps are especially helpful for people with sensitive or reactive skin.

Goat milk soap takes that a step further. Naturally rich in fats, proteins, and lactic acid, goat milk helps soothe inflammation, support the skin barrier, and keep pH levels balanced. 

For anyone dealing with flaking, tightness, or post-wash redness, this can make a visible difference.

At Legend’s Creek Farm, we triple-mill our goat milk soaps to ensure consistency and eliminate excess moisture, which also reduces the chance of irritation. 

We use fully-reacted sodium hydroxide in our formulations, meaning every bar has gone through complete saponification. Our recipes are superfatted with nourishing oils, and we never rely on synthetic stabilizers or harsh chemical preservatives. 

If you’re extremely sensitive, we offer unscented versions that skip fragrance altogether.

Concerned about using sodium hydroxide-based soap on your face? 

That’s valid. Facial skin is thinner and more reactive than the body. It’s smart to patch test first and opt for formulas made with sensitive skin in mind. Choosing a bar that’s thoughtfully made makes all the difference, not just in how it feels, but in how your skin responds.

What’s Really Causing Irritation, Is It the Lye or Something Else?

It’s easy to blame sodium hydroxide for every adverse reaction to soap, after all, it’s the most intimidating name on the label. 

But in most cases, irritation doesn’t come from the sodium hydroxide itself, especially in properly cured soap where it no longer exists in its original form. Instead, the issue often lies with other ingredients that fly under the radar.

Fragrance oils, even natural ones, are a top offender. 

They can contain allergens or compounds that trigger redness, itching, or breakouts, particularly on the face, where skin is more delicate. 

Essential oils like citrus, cinnamon, and mint may smell lovely but are known sensitizers for many people. Similarly, additives like rose clay, charcoal, or botanicals can dry out the skin, even though they’re marketed as purifying or detoxifying.

The answer likely has more to do with the simplicity of those products. Less complex formulas reduce the number of potential triggers. 

In contrast, soaps, especially artisanal bars, often include multiple oils, clays, and fragrances, which means more opportunities for a reaction.

Skin chemistry is incredibly individual. What leaves one person glowing can leave another inflamed. That’s why we recommend introducing new products one at a time through patch testing. Pay attention to how your skin feels immediately after rinsing. 

If you experience discomfort, don’t just look for “sodium hydroxide” on the label, consider what else might be at work.

Choosing the Right Soap When You’re Lye-Wary

If you’re cautious about using soaps made with sodium hydroxide, it makes sense to seek better transparency and gentler options. 

The goal isn’t to avoid lye entirely, it’s to choose soaps made with intention, care, and complete saponification. Whether you have sensitive skin or simply want to avoid unnecessary irritation, a few shopping guidelines can help you find products that align with your needs.

• Cold or hot process soap that has been fully cured (usually 4–6 weeks) to ensure all lye has reacted.

• Skin-loving ingredients like shea butter, olive oil, or goat milk, which help hydrate and soothe.

• Avoidance of synthetic detergents, foaming agents, or opaque “fragrance” labels that hide allergens.

• Fragrance-free options if your skin is reactive or allergy-prone.

At Legend’s Creek Farm, our triple-milled goat milk soaps are crafted to meet the highest standard of skin safety. 

We use fully-reacted sodium hydroxide, no synthetic stabilizers, and add nourishing oils to protect and soften. When formulation and ingredient integrity come first, your skin can feel the difference.