A Closer Look at Sodium Hydroxide

Sodium Hydroxide (NaOH) is a water soluble white which occur in flakes, pellets, granules and powders. Sodium Hydroxide is commonly used in the formulation of bath products, cleansing products, shampoos and shaving products.  Sodium Hydroxide is also used to hydrolyze fats (as in saponification) and form soaps. It is also known as caustic soda and soda lye.

Sodium Hydroxide is created via electrolysis of sodium chloride.  Sodium Hydroxide is a strong alkaline substance that dissociates completely in water to sodium and hydroxyl ions. This creates a strong exothermic reaction when it is added to water.

Sodium Hydroxide is an inorganic base, which means it is an alkali containing no carbon atoms. Sodium Hydroxide separates into cations (positively charged sodium) and hydroxide anions (negatively charged) when added to water and the hydroxide anions decrease the acidity of the water (increasing the pH).  This is why Sodium Hydroxide is commonly used as a pH adjuster in formulas.

Concentrated Sodium Hydroxide is a strong irritant and corrosive to the skin, eyes, respiratory tract and gastrointestinal system if ingested. The severity of effects caused by Sodium Hydroxide is a function of the concentration, the pH, the length of tissue contact time and local conditions and skin type.  Protective equipment such as rubber gloves, safety clothing, face mask and eye protection should always be used when handling Sodium Hydroxide or its solutions.  Proper ventilation should always be used when handling or reacting Sodium Hydroxide.  Sodium Hydroxide should be stored in airtight containers because it readily absorbs the water in the air.

Consumers won’t come in contact with dangerous unreacted lye in cosmetics and soaps.  In the case of soap the Sodium Hydroxide is a reagent. A reagent is a substance that is used in a chemical reaction to produce other substances.  Sodium Hydroxide is used to cause a reaction called saponification to create soap. Sodium Hydroxide is completely safe after it has been combined with other constituents to create an effective, safe, and diverse cleaning agent known as soap. There isn’t un-reacted Sodium Hydroxide in the finished soap because a new product has been formed.

The FDA includes Sodium Hydroxide on its list of substances affirmed as GRAS for direct addition to food.  The Joint FAO/WHO Expert Committee on Food Additives has not limited the Acceptable Daily Intake of Sodium Hydroxide.  Sodium Hydroxide is listed in the Cosmetics Directive of the European Union (see Annex III), and may be used at the specific concentrations, pH values and warning labels when it is used in nail cuticle solvents, hair straighteners and in depilatories.  It can be up to pH 11 for other uses as a pH adjuster.

You should always have a current Material Safety Data Sheet (MSDS) on hand when using Sodium Hydroxide

  • Anonymous

    Concentration is important!

  • Missmisnomer

    I read on one of the body shop products (a body polish) that it has sodium hydroxide. Why would they have needed to add that? They haven’t mentioned the concentration on the package, but ain’t it an irritant to sensitive skin?

    • Dene Godfrey

      Sodium hydroxide is usually added to a formulation for one of two reasons – one is the saponification mentioned in the article, and the other is as a neutraliser for excess acid (if that may be an issue in the formulation). Either way, even though it is listed as an ingredient, it is unlikely to actually be present as sodium hydroxide, as any small excess over that required for the saponification/neutralisation will, over time, react with carbon dioxide in the air to produce sodium carbonate. You are extremely unlikely to get any irritant response from a cosmetic product with sodium hydroxide.

      • Missmisnomer

        Thanks for the prompt reply Dene. That does answer my question.

  • »-(¯`v´¯)-»Soullurre

    So, Sodium Hydroxide is Alkali (NaOH)? I use Bali Soap and in all of their soaps they use this. It’s perfectly fine for hair? I’ve washed my hair with Bali Soap. I have Bali Soap Cinnamon and Vanilla.

    The overall ingredients for the Cinnamon:
    it’s Palm Oil, Coconut Oil, Water, Alkali (NaOH), Cinnamon Fragrant Oil, Paprika Powder, Milled Rice Husk, Cinnamon Powder.

    and for Vanilla it’s:
    Palm Oil, Coconut Oil, Water, Alkali (NaOH), Vanilla Fragrant Oil, Paprika Powder, Rolled Oats, Crushed Vanilla Bean,

    Is this all perfectly fine? I have very sensitive skin and scalp so I just use Bali soap for my whole body.

    • Dene Godfrey

      “Alkali” is a generic term that is by no means specific to NaOH, and it is not the correct INCI designation, so the ingredient listing is (slightly) incorrect. “Alkali” is a noun; “alkaline” is the adjective, describing something having a pH great than 7.0. More importantly, despite your sensitive skin and scalp, you seem to be using Bali soap without any problem, so there is no reason not to continue using it. Whilst NaOH is listed as an ingredient, it is not present in the final product in that form because it reacts with the palm and coconut oils (this reaction is what produces the actual soap) – hence the lack of irritation on your skin.

      • »-(¯`v´¯)-»Soullurre

        Aaaah, okay. Thanks for clearing that up. I’ve asked other people and no one didn’t even respond. That’s great to hear because I hate using shampoo in my hair and just rather use nothing but Pure Unrefined Coconut Oil and Bali soap.

  • please reply

    is sodium hydroxide safe in eyedrops?

  • Sylvi

    Sodium Hydroxide is a one of the ingredient
    s in Euthymol tooth paste, is it safe to use?

    • Dene Godfrey

      Hi Sylvi – if it wasn’t safe, you would know about it fairly quickly! It won’t be present as sodium hydroxide as it will have reacted with any acid present to form safe substances and, anyway, why would a manufacturer make an unsafe product?

  • Sylvi

    ;) thank you for quick answer, well, we have a lot toxic ingrendiens in food(aspartam for example, E 250 ,etc)…and a sodium hydroxide has rather bed opinion;) so i am curious-some of it it will get into a blood stream, how will the body cope with that?I can’t find any info , except the one that says only the bed stuf about it:)

    • Dene Godfrey

      Wherever you look., you will find “bad stuff” about almost every single ingredient in every single industry, because virtually nothing is safe at all concentrations (and everything IS safe at a low enough concentration) – it’s all about the context. If you put concentrated sodium hydroxide on your skin, it will burn you. It is usually added to products to adjust the pH; it does this by reacting to form other substances. For example, if you react sodium hydroxide with hydrochloric acid (both very nasty substances in concentrated form), you get sodium chloride – common salt, which is safe (unless you eat too much, in which case you get water retention and high blood pressure). Also, sodium hydroxide reacts with carbon dioxide (from the air) to form sodium carbonate, so any unreacted sodium hydroxide that may be left in a product (usually almost zero anyway) will not pose a safety issue. Food and cosmetics manufacturers don’t put “toxic” materials in their products at levels that are dangerous, at least, not as far as current knowledge allows. If/when new and credible evidence appears to prove a risk, the permitted levels are either reduced, or the ingredient is banned.

      • Sylvi

        Hi Dene, thank you:) ok, i understand, but..;) it’s very easy to overdose-example-most of the companies use the exact maximum dose they can use to keep the product safe, so if you eat food that contains preservatives,it’s a hight propability that you intake more then you should by eating to many products containg the same bad stuf ;) my worry is that this may happen with cosmetics aswell.;)

        • Dene Godfrey

          Hi Sylvi – I am not sure if that’s really true for food, but it certainly isn’t true for cosmetics. Most ingredients don’t have a maximum limit, and those that do (preservatives, for example) are rarely used at the limit, in my experience.

          • Sylvi

            Thank you so much for your time:)

  • may

    How could they use (NaOH) in women’s vaginal products, and have it deemed safe by the FDA ?

  • Holly

    I’m using a 2% BHA liquid facial exfoliant that uses Sodium Hydroxide as a pH adjuster at a concentration of 1.05%. The company tells me the low concentration will not cause irritation. Is this really a safe amount to be putting on my skin?

    • http://www.sterlingminerals.com/ Katherine

      Hi Holly,

      Sodium Hydroxide is primarily used for saponification of butters and oils to create soaps. It is also used as a buffering agent such as to adjust and neutralize the pH of something. As far as the ratio, I would be concerned with its use in a product using Salicylic Acid which is usually what comprises the majority of your BHA products. This alone can cause irritation of the skin and SH is a known skin irritant. Personally, I wouldn’t use this ingredient on my face at all, or my skin. Many other great cleansers out there that don’t use SH, you’ll just need to keep an eye out for one if BHA is something you require to use on a regular basis.

      Good Luck!

      • Holly

        Thanks! I do need to use BHA for acne and I found a product that doesn’t contain Sodium Hydroxide.

  • Bekah

    is this dangerous in the oils we use????