Soap, Methylisothiazolinone, Methylchloroisothiazolinine, and Pentasodium Pentetate?

Updated: May 28


Growing up, all we had was bar soap. You get it wet before you put in on your skin.  Then, make sure you washed if off. The bacteria, dirt, and excess oils get washed away. It’s how we clean ourselves.

I prefer bars of soap in the shower because it is easier to use and I get more for my money. Liquid soaps I tend to go through faster. Are they bad for you? No, some may prefer liquid soap.

In a study (1),  no evidence soap bars spread any infection. So, what is the benefit of bar soap? I say it depends on what is in the soap. Many soaps in liquid, and solid form contain detergents. Often drying your skin so you need moisturizer. Some have moisturizers in their product. Some have chemicals even I, as a nurse, have a hard time pronouncing. It doesn’t necessarily mean the are bad for you. Merriam Webster says it is “a cleansing and emulsifying agent made usually by action of alkali on fat or fatty acids and consisting essentially of sodium or potassium salts of such acids” (2).

All soaps use a fatty acid, typically a surfactant. OK. I will keep if brief and easy! What is a surfactant? Well the word originates from the term surface acting agent (2). It is an agent that lowers the surface tension. A surfactant works between liquid-liquid, gas liquid, and solid-liquid. The higher the surface tension the more cohesive or stuck together they are. It makes the surface stronger. When you are trying to clean something, it means it is harder to remove the surface of bacteria or dirt harder. So, a surfactant decreases the surface tension making soap and water remove bacteria and dirt easier. Good if you want to cleanse yourself right?

Herbal Soap

Herbal soaps contains all natural products. Are soaps bad if they are not herbal? No. It depends on what is in the soap. An emulsifier is something that can bind oil and water. I think your chances of removing dirt, toxins, and bacteria/viruses are better if you wash with a surfactant and an emulsifier.

What is Herbal Soap?

It’s an oil or fat (either from an animal or plant) mixed with a compound called an alkali. Most of us know what an acid is. It is something with a low pH (<7). An alkali is something with a high pH (>7). Our blood ranges from 7.35-7.35. Our stomachs are 1.5-3.5. The pH of our skin is around 4.7-5.5.  The purpose of using an alkali on your skin is simply not to burn it.  The lower the pH the more acidic it is. The alkali is used in cleaning your skin.  What you want is to cleanse your skin and keep the pH at the same level when you are done. The pH of lye soap can range from 7-10.  The general rule of thumb is to make soap for sensitive skin, you want to keep the pH between 8-9.  How do you do it?  Recipes for soap will have less lye in them.

Basic herbal soap includes : Animal fat or vegetable oil. Pure lye (alkali), distilled water, essential oils, colorants are optional and make the soap look more appealing. The colorant would come from a natural source. Some think alcohol is needed ( commonly rubbing alcohol 91%). If you don’t mind the bubbles, it is optional. The FDA does have some guidelines regarding the use. Lulu’s prefers not to use it. We don’t mind the bubbles and there are other ways to minimize them.

Shea Butter or Double Shea Butter: The “butter” comes from the fats of the Shea tree. It doesn’t clog your pores, not know for allergic reactions, and used for all skin types. Shea butter moisturizes your skin without making it oily. Used for it’s antibacterial, antifungal, antioxidant, and anti-inflammatory qualities. The fatty acids are thought to remove excess sebum while moisturizing your skin. Shea butter has triterpenes. This compound is thought to stop the destruction of collagen.

Honey Glycerin: Glycerin and honey are humectants. These humectants draw water or moisture from the air into your skin. Glycerin is used to help prevent loss of moisture in your skin. It also can create a skin barrier to protect your skin. Glycerin soap may have a lower pH which may help your skin stay moist and bring down the alkalinity of lye soap. Honey is pretty well known for it’s antimicrobial, antioxidant, and anti-inflammatory properties.  It is thought to be beneficial for some inflammatory skin conditions.  

Still afraid to put lye on your skin?  Well let me tell you a secret. Lye, in soap making, basically converts ingredients into soap. The process is called saponification. Saponification is “the act, process, or result of making soap :conversion into soap” (3). Lye is sodium hydroxide when making a bar soap (also used as potassium hydroxide). When it’s mixed with oil, water, and other compounds they are all converted into soap. In the end there is no Lye in the product.

Most essential oils are added. Depends on what you want. If you want a scent, your favorite one is fine. Common essential oils for skin health are lavender, frankincense, citrus, rose, plantain, calendula, and chamomile. You can pretty much add whatever essential oil is good for use on your skin.  Now we teach you essential oils should not be put directly on your skin.  You need a carrier oil. A carrier oil is typically a fatty oil made from a plant.  They usually come from kernels, nuts, or seeds.  They are also called base oils or vegetable oils.  They will dilute the essential oil so it doesn’t irritate your skin and allow the benefit of the herb to absorb into your skin. 

Remember I talked about oils?  What can you find in “natural”  or herbal soap? Commonly you will see Goat’s Milk soap base, an oil or fat like coconut, Palm oil, or glycerin. Purified or distilled water, sodium hydroxide. Sorbitol, propylene glycol, and titanium dioxide. Often other compounds are added for a specific purpose. It doesn’t mean they are not natural. You do have to be careful. Some soaps on the market qualify to be called detergents

Don’t remember your chemistry days? Here is a condensed version: I know I have picked up many things in the store and looked at the ingredients. At some point I put the product down because I had no idea what was in there and honestly had a hard time pronouncing it. Some times, some of those chemical compounds come from nature.  Not all of these compounds we can’t even pronounce are not bad for you and are used for a specific purpose. For me, then it’s ok. I was at an impasse looking at all these chemical names. I didn’t even know what these chemical names were and I had taken years of chemistry classes! What would I do at work when I was a staff nurse? Look it up. So I did. Come to find out, with many soaps (and other products), they are there for a purpose.

What Are All Those Chemicals?

Propylene glycol: I hear good and bad about it. What do I know. It comes from natural gas. It is synthesized by using two organic compounds by heat and hydration. Why use it? It is used as a humectant meaning to keep moisture in your skin. The Cosmetic Ingredient Review (CIR) works with the FDA to review ingredients in cosmetics. They are made up of scientists, toxicologist, and dermatologists to name a few. The amounts allowed are considered safe by the CIR. They can however be irritants. I would be weary of products not made with pharmaceutical grade glycol.

Sodium stearate: Found in vegetable oils. It is also found in animal fat. It’s been the base of soap for thousands of years. One of the most common fatty acid salt in today’s soaps. Why use it? It is needed to stabilize, harden, and thicken soaps. Instead of synthetic preservatives it is a natural one.

Stearic Acid: Another saturated fat. Used in soap to clean, remove oil, dirt, and bacteria. Sodium laurate/sodium lauryl acid/laurie acid (sodium salt of lauric acid): It’s is used in soap to clean your skin, act as a surfactant, and emulsify your skin. The surfactant decreases the surface tension between water and in this case your skin. What does it mean? If makes foam to help the water take away things like bacteria. Your lungs actually makes surfactants to clean out your lungs. The purpose of emulsification is to bind the oils and water used to make soap. What should you know? They are fatty acids which come from plants like coconut, laurel, and palm kernel. Yup, naturally occurring.

Sorbitol: is an alcohol from a sugar base. Why is it used? for a few reasons. It helps to hydrate and moisturize your skin. It’s used as a prebiotic. What is means is it feeds good bacteria on your skin. Just like your gut has good bacteria. They help your skin stay moist, regulate normal oil production, and fight off free radicals. Where does sorbitol come from? Berries like blackberries, strawberries, raspberries, apples, avocados, and cherries. Yup, also from natural sources.

Sodium chloride: also known as salt. Why add it to soap? A few good reasons. Chemically, it makes fatty acid salts in the soap. In English, it helps stop the soap from drying out your skin too much. It also helps to exfoliate your skin. Yup. also, from natural sources.

Silica (Silicon dioxide): is a mineral commonly found in quartz and sand. It’s one of the most common of the elements, chemically speaking. You can find versions of it in toothpaste. It’s is used in soap making to stop something called soap sweat or also known as glycerin dew. Remember how I said glycerin is a humectant. Great to put on your skin to draw moisture. The down side. It will draw moisture to the soap. Silica helps to stop the moisture forming on the soap. Yes, also natural.

Titanium dioxide: is a natural element used to lighten soap and make them look “prettier”. It is also in most sunscreen. It is used to protect against UV light.

Methylisothiazolinone and Methylchloroisothiazolinine:  Methylisothiazolinone is an organic compound used in “green” cleaning products and personal care products like soap. It is an organic preservative or antimicrobial. It is determined by the Cosmetic Ingredient Review (CIR) to be safe in soap and skin care products (7). If not used as directed can cause contact dermatitis and allergic reactions (8). 

Pentasodium Pentetate?  Pentasodium pentetate is the salt from Pentetic Acid (4) . Used as something called a chelating agent. What it does is prevent metal ions from water from forming soap scum.

Tetrasodium etidronate: another chelating agent (5). Also known as a water softener. I have seen sites calling it cancer causing. In large doses or not taken as directed it is a corrosive and irritant (6), not cancer causing.

Magnesium chloride: is added to soap to help with hard water. You can find it in sea water. It help with foaming. Why is foaming in a soap important? Remember the word surfactant. It helps the water take away things like bacteria, sebum (oil on your skin), and dirt when washed away. Magnesium nitrate is a naturally occurring mineral. It is often found in goat’s milk products.


Most of the ingredients which are chemical compounds and hard to pronounce are found in soap bases like glycerin and goat’s milk. They are most often naturally occurring, derived from plants, animals, or minerals. They each have their role in cleaning your skin. What is important to know before you use these products or any other products remain the same. Do you have allergies and make sure your rinse. Check if it irritates your skin. Our skin is suppose to be at a certain pH. Maybe yours is, maybe it isn’t. I have read on various sites selling products, some of these compounds being called cancer causing and toxic. Well if you drink liquid soap no good will ever come of it. The above compounds are not toxic if used as directed.  The claims have been disputed and declared safe by reputable boards whose purpose is to make sure what we are using is safe. These compounds have no cancer causing agents and have a purpose in soap. Now, they are used on your skin. So if you have allergies or don’t use as directed,  be wary.

Soaps and cosmetics are governed by the FDA or Consumer Product Safety Commission and Cosmetic Ingredient Review Board (CIR). I go to the best source. Places like Pubmed, NIH, and Pubchem. These are what are called information clearing houses. Meaning studies, material safety data sheets (MSDS) are found. To be approved by the FDA, you have to go through sometimes years of studies. The material safety data sheet (MSDS) is the resource for anyone who works with chemicals. 


1. Heinze, J. E., & Yackovich, F. (1988). Washing with contaminated bar soap is unlikely to transfer bacteria. Epidemiology and infection, 101(1), 135–142. Saponification | Definition of Saponification by Merriam-Webster (merriam 3. Soap | Definition of Soap by Merriam-Webster ( 4. Benes DM, Burnett CL. Final report on the safety assessment of pentasodium pentetate and pentetic acid as used in cosmetics. Int J Toxicol. 2008;27 Suppl 2:71-92. doi: 10.1080/10915810802244546. PMID: 18830865. 5. National Center for Biotechnology Information (2021). PubChem Compound Summary for CID 19629. Retrieved February 15, 2021 from 6. National Center for Biotechnology Information (2021). PubChem Compound Summary for CID 3305, Etidronic acid. Retrieved February 15, 2021 from 7. 8. National Center for Biotechnology Information (2021). PubChem Compound Summary for CID 57269290, Methylisothiazolone. Retrieved February 15, 2021 from 9. (Lauren, n.d.)

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