Linear Sulfonate

Q. I just bought a natural cleaner and it contains LINEAR SULFONATE. Do you know anything about this? I have seen it compared to SLS's but maybe as a better option? I just want to make sure that it is not as equally carcinogenic - or that it is not bad!


A.  Thanks for your question, Tiffany! 

It turns out that "Linear Sulfonate" is not just one chemical, but a blend of several chemicals all in the same family.  I'm assuming the product you're looking at is Biokleen, as they claim on their website "Linear Sulfonate is a propriety blend of vegetable based surfactants."  While their blend is proprietary (read: not disclosed), we can take an educated guess at what this "Linear Sulfonate" is. 

There is a group of surfactants (detergents) that are called Linear Alkylate Sulfonates.  Traditionally, a blend of compounds are sold under the name Linear Alkylbenzene Sulfonate (commonly abbreviated LAS).

  • Decylbenzene sulfonic acid, sodium salt
  • Dodecylbenzene sulfonic acid, sodium salt
  • Tridecylbenzene sulfonic acid, sodium salt
  • Undecylbenzene sulfonic acid, sodium salt
  • C10-16 Monoalkylbenzene sulfonic acid, sodium salt
  • C10-13 Alkylbenzene sulfonic acid, sodium salt
  • C10-14 Alkyl deriv benzene sulfonic acid, sodium salt
  • C10-14 Monoalkylbenzene sulfonic acid, sodium salt
  • C10-13 Alkyl deriv benzene sulfonic acid, sodium salt

This blend of chemicals commonly known as LAS is likely what this "Linear Sulfonate" listing refers to. 


LAS can be acutely toxic when ingested or applied to skin at very high amounts.  It is most toxic when inhaled in powder form, with mortality occurring at a particle concentration of 310 mg/m3.  This concentration would likely only happen in an industrial setting, however, not posing a risk in household use as you would use it in a dishwasher or laundry soap.


At low concentrations (up to 2.5%), LAS typically does not exhibit skin irritancy, but at 5% it's moderately irritating and severely irritating at a 50% concentration.  Eye irritation can occur as well, but is easily reversed by flushing with water.  This study found it to be less absorbable by skin than SLS. (Source)


Not found to be a carcinogen or mutagen.

Reproductive Toxicity

Not found to be a genotoxin or estrogen mimicker.  However, in high amounts, it was found to increase the estrogenic effects of other pollutants in aquatic life. (Source)

It is found to be highly toxic to acquatic life, but is also highly biodegradable. (Source)

So, all in all, as long as you're not exposed to high amounts of LAS, I would consider it to be relatively safe as used in a laundry detergent or dishwasher soap.  Because of its irritancy and potential for moderate toxicity, however, I would avoid it in a personal care product. 



Linalool is a component of many essential oils, including orange, lavender, rose, rosewood, and coriander.  The main problem the Cosmetics Database has with linalool is the risk of skin irritation and allergic reactions.  Just like limonene, linalool is not a skin allergen in its pure form.  However, when it's oxidized, it can cause allergic reactions/sensitivity at high concentrations.  (Source

Also, like limonene, pure linalool has anti-cancer effects.  One study found that "...linalool exhibited comparable IC(50) values to the commercial drug vinblastine on the ACHN cell line" in killing liver cancer cells.  (Source)

This study found that linalool "may improve the therapeutic index of anthracyclines in the management of breast cancer, especially in MDR tumors."  In other words, it aided breast cancer drugs in killing breast cancer cells that had grown resistant to the drugs.  (Source)

Linalool also shows promise against leukemia. Among the substances tested "linalool showed the strongest activity against histiocytic lymphoma cells U937 (IC50: 3.51 microg/ml, SI: 592.6) and Burkitt lymphoma cells P3HR1 (IC50: 4.21 microg/ml, SI: 494.1)."  (Source)

So, again, we get back to the point that the Cosmetics Database doesn't give an accurate or full picture of linalool because it doesn't factor in the positive information.  Yes, oxidized linalool can cause skin reactions, but as long as the essential oil or linalool extractive is pure and fresh, it is not just safe, but beneficial.



Q. I love having essential oils in my bath & body products. I think they are a great alternative to synthetic fragrances due to phthalates, etc. I know that some essential oils contain naturally occurring components such a limonene and linalool. EWG's Skin Deep database rates these components poorly. I'm guessing it's because some people can have skin sensitivities to them. I'm not one of those people so I don't mind essential oils that naturally contain them. My issue with it is that when companies choose to list these components they sometimes get a poorer rating on their products posted on the database. Is it because the components have synthetic versions too? I feel like essential oils are unnecessarily being given a bad name. Can you please shed some light on this subject and help people to understand whether these components are good or bad?



A.  Hi Victoria--I think that's a wonderful question!

First, let's look at limonene, one of the major constituents of orange essential oils.  Limonene is typically not made synthetically because it is so cheaply and easily sourced from the orange industry. But on a molecular level, synthetic and natural limonene are identical.  It's possible that synthetic limonene can contain traces of contaminants, but for the most part, synthetic and natural act the same. 

The Cosmetics Database gives orange essential oil a "0-1" score, depending on the variety of orange.  But limonene, the major constituent gets a scary-looking "6."  Now, wouldn't it make sense that orange essential oil should score similarly, given that orange essential oil is 90 percent or more limonene? 

The discrepancy lies within how the Cosmetics Database works.  The Database is basically a collection of databases, gathering its information from about 50 other data sources.  Most of these databases pertain to workplace safety.  Limonene is much more widely used in industrial applications because it's cheaper than buying whole orange oil, so it shows up a lot more in these industrial databases.  But whole orange oil isn't used as much in industrial applications, so there is a lot less data, and thus, a lower score. 

So, does that mean that orange essential oil should score higher, like limonene, since orange essential oil is 90% limonene?  Is orange or any oil that contains limonene oil dangerous?

Let's look at the score for limonene in the Cosmetics Database. 

The biggest problem that the Database has with limonene is "allergies/immunotoxicity" and "irritation, (skin, eyes, lungs)."

One of the biggest source databases for the Cosmetics Database is HAZMAP, an occupational safety database, which, in turn, draws its information from the National Library of Medicine.  So, let's look at some actual source data. 

It turns out that the vast majority of the problems with limonene happen when the compound is oxidized, or turned rancid.  "Studies in guinea pigs revealed that air oxidized d-limonene, but not d-limonene itself, induced contact allergy." (Source)  In the 1960s, various citrus oils were studied for their tumor promoting effects.  Undiluted citrus oils were applied to skin that had been treated with a cancer initiator.  The citrus oils promoted the growth of the tumors (some malignant, some benign).  A few years later, it was discovered that only oxidized limonene promoted tumor growth.  (Source

In fact, the Cosmetics Database states that, "Upon storage and exposure to sunlight and air, limonene degrades to various oxidation products which act as skin and respiratory irritants and sensitizers."  So, it does acknowledge that it's not limonene itself that's problematic, but the compounds it turns in to when it turns rancid. 

And, in fact, several new studies have found limonene and citrus oils to have anti-tumor effects, preventing the growth of many types of tumors in animals treated with cancer initiators.  Here are just a few statements from different studies:

"D-limonene, which comprises >90% of orange peel oil, has chemopreventive activity against rodent mammary, skin, liver, lung and forestomach cancers." (Source)

D-limonene and other monoterpenes '"act through multiple mechanisms in the chemoprevention of mammary and other cancers." (Source)

"These results suggest that the monoterpenoid d-limonene might be a chemopreventive agent for colonic carcinogenesis in rats." (Source)

D-Limonene and other monoterpenes "are effective, nontoxic dietary antitumor agents which act through a variety of mechanisms of action and hold promise as a novel class of antitumor drugs for human cancer." (Source)

Robert Tisserand, one of the foremost researchers in the field of essential oils study states that, "Although even oxidised citrus oils are very unlikely to present a hazard in aromatherapy, this research very much underlines the importance of using relatively fresh essential oils, which have not oxidised."  [Essential Oil Safety, Tisserand, 1995]

So, how can you tell if the orange oil or limonene in the products you're using are oxidized or not?

The use of oxidized orange essential oil in a personal care product is likely not to pose any significant threat because the negative effects primarily apply to being exposed to full-strength limonene over extended periods of time.  But, if you want to play it safe, there are some simple things you can do to ensure the freshness of the product.  One thing to look for is the addition of rosemary extract or vitamin E.  Both ingredients are powerful antioxidants that help to keep the orange oil/limonene fresh.  Second, would be the smell.  If it smells like a fresh orange, lemon, or lime, it's likely fresh. Third, follow the manufacturer's shelf-life dates.  And fourth, if there's a question, ask the manufacturer about the freshness of the ingredient.  (A personal note: As a certified organic processing facility, at any time, anyone can ask us about any ingredient--from your ordering records we can tell you any certifying agency of the ingredient, the lot number of the ingredient, and the date of manufacturing/harvest for that ingredient, and the manufacturing date and batch number of our product.  We order our ingredients frequently and in small amounts, and make our batches in small amounts to ensure freshness.  Typically, when you order from us, the product you order has been made in the last two weeks.  We are very careful to store all our essential oils away from sunlight and heat, so we can give you the freshest products possible.)

I hope that begins to answer your question, Victoria.  As I've said many times before, the Cosmetics Database is a great place to start, but it can be incorrect or incomplete.  Because it only factors in negative information and doesn't consider issues of freshness, you don't get a full picture of the ingredient.  With its promise for being a treatment or prevention method for cancer, limonene is not only safe when used in a pesonal care product, its benefits are far-reaching. 

Tomorrow we'll take an in-depth look in to the second compound you mentioned, linalool.  



Q:  What about soy lecithin in lotion? Soy acts as estrogen in the body, right? Is it safe for external use? Thanks so much!


A.  That's a great question, Kelly! The active weakly estrogenic compounds in soy are called isoflavones. The jury's still out on isoflavones, as some studies have found them to be helpful in preventing breast cancer, but other studies have found them to contribute to estrogen dominance.  That aside--there are no isoflavones in lecithin.  The fats are pressed from the seed to create soybean oil, which is just comprised of fatty acids, no isoflavones) and then the lecithin is further extracted from the oil.  Lecithin exhibits no estrogenic effects, and is actually a vital nutrient in the body, present in our cells' membranes. 


What is "Natural?"


Dave asks: Is it bad to have synthetic ingredients, if they are derived from natural ingredients?  I guess I always thought synthetic meant "fake" or "bad"?  Could you explain what synthetic means?

Patrick comments: This eternal moaning about "chemical" and "natural" points out how little people understand about their physical environment. Nature also synthesizes substances because everything that exist has once been made, created or synthesized. So "synthetic" is natural and vice versa. All materials belong to our physical dimension and it's all just a matter of rearranging atoms. It appears as if people think that chemistry is some kind of man made evil invention but nature can not circumvent its own laws of chemistry and physics. Nature IS chemistry.

So: What does "synthetic" mean?  How can one tell if something is "natural?"  And does being synthetic always mean "bad" and does being natural always mean safe?

Answer: There really is no legal definition of the term "natural."  One could argue that everything in the world is natural.  Humans are natural beings, so what we create is part of nature.  Just as a beaver would build a beaver dam, our creations are natural, too.  By this definition, oil refineries, plastics, BPA, pesticides, and GMO crops are all natural.  And, as Patrick points out, synthesis is the basis of life.  Anything that has been created, has been synthesized.  So, anything alive is "synthetic" because it has been synthesized by cells and DNA and enzymes.  Thus, by these definitions, natural is synthetic, and synthetic is natural. They are one and the same.

But in the realm of personal care products, the divide between natural and synthetic is much more specific.  Because our bodies are fragile systems, we want to put things in them and on them that are beneficial and that work within our own bodies' systems. For this reason, a differentiation between synthetic and natural must be made because it can be a general guide for health and wellness. (I say general, because, as I explain below, not all natural things are safe, and not all synthetic things are dangerous).

I consider an ingredient to be natural if it is a raw material or is only one chemical reaction away from the raw material. So, for instance...

Coconut oil is a raw material.  It is physically extracted from naturally-occurring coconuts. Coconut oil is natural.

Coconut oil is used to create soap.  There is one chemical reaction that occurs: coconut oil combines with lye to create a new compound we know as soap.  

Coconut Oil > Soap

One step, one chemical reaction.  By my definition, soap is natural.

Now let's take a look at a chemical that I consider to be synthetic: Sodium Lauryl Sulfate.  Sodium Lauryl Sulfate takes many more steps to create from the original coconut oil.  First, coconut oil is reduced in to lauryl alcohol.  Lauryl alcohol is then reacted with sulfuric acid, then reacted with sodium carbonate.  The chemical steps look like this:

Coconut Oil > Lauryl Alcohol > Hydrogen Lauryl Sulfate > Sodium Lauryl Sulfate

Here we have four chemical reactions that occur, so I consider Sodium Lauryl Sulfate to be synthetic.

Some companies will bill it as natural because it was once coconut oil.  But, by my definition, it is a synthetic because of the numerous chemical reactions that have to take place in order for it to be created.  So, let's take a look at another example. 


Tocopherol is extracted from soybean oil via a vacuum.  There is no chemical processing, this is a simple physical method.  No chemical reaction has occurred from the original substance.  So, by my definition, Tocopherol is natural.

Tocopherol acetate

Tocopherol is turned in to tocopherol acetate through 7 different chemical reactions, which you can see here:File:Synthesis Tocopheryl acetate.svg

Thus, by my definition, Tocohperol acetate is synthetic.

Does "Synthetic" mean "Bad?"

Synthetic doesn't always mean bad. We use one synthetic ingredient--decyl polyglucose, in our salt scrubs as a lathering and cleansing agent.  Other salt scrubs are just salt and oil, so they don't clean and they leave an oil slick in the bath. We wanted to make ours cleanse, so we used decyl polyglucose.  Of course, there's castille soap, but when you add soap to salt it turns to mush.  So, because we couldn't use soap, we use the polyglucose. It's made from sugar & corn, has no known risks, has been tested extensively for safety, and scores a 0 risk in the Cosmetics Database.  

In make-ups, there are synthetic mineral pigments and there are natural mineral pigments (iron oxide, etc).  Oxides created in labs are generally considered to be more safe than natural oxides because they have a higher level of purity.  Natural oxides can contain traces of lead, which, even though it's a naturally-occurring substance, is toxic to us.

And natural doesn't always mean that an ingredient is safe. There are several essential oils that are highly toxic.   Uranium could be considered natural (it occurs naturally in the ground) but it's obviously not safe. 

Natural vs. Organic

Ingredients that are considered natural can still be genetically modified, grown with pesticides, boosted with fertilizers, or otherwise processed with synthetics.  When an ingredient or product is organic, it means that it has been grown, harvested, and processed without these things.  With USDA certification, you can be sure that companies are fully disclosing their ingredients and not sneaking in synthetics under a natural-sounding name, like Japanese Honeysuckle Extract which contains synthetic butylene glycol, or Grapefruit Seed Extract which is actually a quaternary ammonium compound.  Organic also means that the product is 95% or more agricultural ingredients.  Certain clays, salts, and other minerals can be present in an organic product, but they do not count towards the organic content. 

Natural Certifications

There are several natural certifications that cosmetic companies can have.  BDIH, NSF, EcoCert, NaTrue, COSMOS, Demeter Natural Products Association, IOS Cosmetics Standard, Whole Foods Premium Body Care.  Each has their own particular standards (and I'm working on an article that will outline the basics of each "seal").  As a general trend, they do allow synthetic ingredients, but the ingredient must have once been an agricultural product (vs. petroleum) and may not have gone through certain synthetic processes, (like ethoxylation).  As opposed to USDA organic certification, they, for the most part, allow micas, mineral pigments, hydrolyzed proteins, and hydrogenated oils (each standard varies and has their own rules) and ingredients may or may not have been grown with pesticides (depending on the certification.) 

The Bottom Line

Something being 100% natural doesn't always mean it's safe.  Something that's 100% synthetic doesn't always mean it's dangerous.  But as a general rule of thumb, natural is better for our bodies.  Our bodies are designed (by evolution or creation, whichever you prefer) to intake foods that are grown from the earth.  Eating an organic apple is obviously more healthy than eating a piece of plastic.  Our bodies are designed to digest an apple and use its nutrients and energy.  But the body lacks the enzymes, cells, and DNA to get any nutrition or benefit from a piece of plastic.  This is where the "natural" vs. "synthetic" difference really comes in to play. While, existentially, plastic could be considered natural, because we as natural beings created it, it has a limited place in aiding the body for health. (One exception would be a prosthetic limb, which generally increases the quality of life for a person.)  Thousands of synthetic chemicals have been created and marketed over a short span of time, and much is not known about their safety to our health.  And the mentality of the cosmetics industry regarding synthetic chemicals seems to be "innocent until proven guilty."  (Take for instance, Dene Godfrey's series on parabens, where, in the face of the SCCS lowering their suggested acceptable concentration of parabens in a product, he heralds it as a victory for the safety of parabens.)  Many people prefer to stick to foods and personal care ingredients that have a hundreds of years as their track record for safety, than to use a synthetic substance that has controversial or conflicting safety data.  The bottom line is, we all have our own standards for what we personally feel comfortable putting in and on our bodies.  Researching and educating yourself about the ingredients around you is the best way to find your personal balance of synthetic vs. natural. 


Do YOU have a question about an ingredient?  Post your question here and I'll give you my take on it!