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Tuesday
Feb152011

Limonene

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?

Thanks,

Victoria

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.  

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Reader Comments (4)

Thank you, Stephanie! This is wonderfully helpful!!!

Fri, March 11, 2011 | Unregistered CommenterVictoria

There's an inherent problem with chemicals such as limonene and linalool. Go down the cleaner aisle of Home Depot and you can smell them through the bottles. The chemicals are being oxidized through the plastic containers as they sit on the shelf. They make me quite ill. Some companies like Glade use them in air fresheners enough though they shouldn't be allowed to oxidize.

Fri, June 28, 2013 | Unregistered CommenterDebra

This was very helpful. I was thinking of putting grapefruit oil it in my homemade deodorant instead of tea tree oil to avoid any future bacterial resistance, and then when I saw the rating on the Ewg Skin Deep website was a 6, I hesitated. Now I feel a little better. Thank you for clearing that up.

Tue, September 9, 2014 | Unregistered CommenterAdriana

Thank you, really helpful post :)

Wed, September 7, 2016 | Unregistered CommenterLiza

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