Unfortunately, between the self-proclaimed beauty “experts” on TikTok and the increasingly blurred line between scientific fact and marketing jargon, the beauty community is rife with misinformation and fear-mongering. At this point, we’ve heard it all—everything from claims that certain hair care products will make your hair fall out to allegations that tanning beds are good for you (they are decidedly not).
And the discourse on product ingredients and formulations might just hold the Pandora’s Box of all beauty misinformation. What’s good for you? What should you avoid? It’s never been a straightforward, simple answer, but it’s become even more confusing with all of the chatter.
So we’re setting apart fact from fiction, one ingredient at a time. Meet sodium hydroxide, a hotly debated skincare ingredient perhaps better known as lye. Yes, that lye. We asked board-certified dermatologists Anthony Rossi, MD, and Joshua Zeichner, MD, to tell us all about it.
Meet the Expert
- Anthony Rossi, MD, is a board-certified dermatologist and laser expert at the Memorial Sloan Kettering Cancer Center in New York City. He is internationally recognized as a leading expert on sensitive skin.
- Joshua Zeichner, MD, is a board-certified dermatologist and the Director of Cosmetic and Clinical Research in Dermatology at Mount Sinai Hospital in New York City.
As it turns out, things aren’t always as they seem. Keep reading to learn why this scary-sounding substance isn’t so bad after all.
Type of ingredient: pH balancer
Main benefits: According to Rossi, sodium hydroxide helps maximize the efficacy of certain products, particularly cleansers and leave-on exfoliants, that require the pH to be held within a very specific range.
Who should use it: While there’s been ample fear-mongering, both dermatologists agree that it is generally considered safe to use in beauty products. That being said, every person is different. Rossi suggests that anyone who is highly allergic or sensitive spot-test the product first on the forearm.
How often can you use it: Since sodium hydroxide is used in cosmetics in very low quantities, it can be used daily without irritation.
Works well with: Since sodium hydroxide is used mainly as a pH balancer, it’s a fairly common ingredient in a handful of formulas, according to Rossi. You’ll generally find it in very acidic and very alkaline formulas.
Don’t use with: Sodium hydroxide works well with most other ingredients. It’s not so much about what it’s used with as much as how much is used.
What Is Sodium Hydroxide?
Sodium hydroxide goes by many names: caustic soda, sodium hydrate, soda lye, and lye. Yes, you heard that right: the lye found in drain cleaners, paint strippers, and silver polish is the same thing as the sodium hydroxide in your favorite cleanser. And yes, sodium hydroxide can be highly corrosive—it can cause severe burns and corrosion in acute exposures. But there’s one major difference between the sodium hydroxide in bleach and the sodium hydroxide in lotion: the concentrations.
In large amounts, sodium hydroxide is absolutely caustic, no questions asked. However, the amounts used in skincare products tend to be so small that they’re generally completely used up in the process of balancing pH levels, and therefore totally fine for you.
Sodium hydroxide also helps saponify oils—in other words, it helps oils and fats lather and foam up in soaps and cleansers. If you like a good lather during your cleanse, you probably like sodium hydroxide.
Benefits of Sodium Hydroxide for Skin
Sodium hydroxide has a select few, but very important, benefits for the skin:
- Balances and maintains product and skin pH levels: Happy skin is pH-balanced skin. By adjusting the pH of a formula, sodium hydroxide makes the formulation kinder on the skin.
- Maximizes product efficacy: Topical skincare products work best at a pH range of 4-6. Beyond stabilizing the pH level of the product and your skin, sodium hydroxide also makes products like these work better.
- Saponifies oils in the soap-making process: According to Rossi, sodium hydroxide helps oils to lather in soaps and cleansers.
In order to fully understand why sodium hydroxide is so beneficial to the skin, we need to talk about pH levels.
As we learned in middle school science class, the pH scale runs from 0 to 14, with anything below 7 (which is pH neutral) considered acidic and anything greater than 7 considered alkaline (or basic). Maintaining a pH level of around 5.5 (or between pH 4 and pH 6) is ideal for balanced skin. At this level, the skin’s acid mantle can effectively act as a layer of protection against environmental factors like allergens, pollutants, and bacteria.
As Zeichner explains, the hydroxide component in sodium hydroxide is basic. So when added to skincare, it alkalinizes the formulation and, in turn, helps establish and maintain that desired pH. Sodium hydroxide is used up as that process occurs, ideally leaving the final formulation with negligible amounts of the original sodium hydroxide.
Because pH balance is so key to great skin, sodium hydroxide can be found in tons of beauty products—both those you wash off and leave on. Rossi goes so far as to call it a common ingredient in the beauty world.
Side Effects of Sodium Hydroxide
We’ve already talked a lot about the potentially scary effects of sodium hydroxide in general. But few, if any, of those concerns are actually present when it comes to the small amount of sodium hydroxide found in skincare.
In an effort to avoid fear-mongering, we’ll leave it at this: Sodium hydroxide can be very harmful when used in large amounts. That being said, the amount used in skincare is so small that it’s unlikely to cause any sort of damage to the skin. And, on the off chance that someone does have a reaction to the sodium hydroxide in skincare, it will cause effects more along the lines of dryness or redness, not a medically serious burn.
As Rossi and Zeichner both underscore, sodium hydroxide is absolutely considered safe to use in beauty products. End of story.
How to Use
Usage depends on the product—follow whatever specific instructions a product gives. That being said, you might want to spot-test it first if your skin is especially sensitive or reactive.
The Final Takeaway
So maybe sodium hydroxide in skincare isn’t going to burn your face off. I mean, beyond the actual science of it all, can you imagine a beauty brand putting out a product that was legitimately unsafe and harmful? Talk about a PR nightmare, not to mention the lawsuits.
The lore around sodium hydroxide is proof that fear-mongering is very real, even if it’s done with the best of intentions. At the end of the day, science never lies, so find the facts and let them lead the way.
Is Sodium Hydroxide Safe in Skincare?
Yes, because sodium hydroxide is used at such a small concentration in skincare, it’s widely recognized as a safe ingredient.
Is Sodium Hydroxide Bad for Sensitive Skin?
Not necessarily. Sensitive skin is reactive in nature, so it might react to sodium hydroxide the same way it might respond to any other ingredient it doesn’t agree with.
How Is Sodium Hydroxide Formed?
Sodium hydroxide is usually manufactured by the electrolysis of a saltwater solution.
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