how toxic is orange oil?

i use orange oil as an all-purpose solvent in my studio.  i use it to mix up my oil paints.  i use it to wash my brushes.  i use it to make wax paste to use in encaustic painting.  i use it as a paint remover and a degreaser and in really tough laundry, and a drop at a time as a flavoring.

i’ve got asthma.  i get all wheezy in the detergent aisle at the supermarket.  i’m sensitive to things in parts per billion, rather than parts per million.  but all orange oil does is make me hungry.

here’s an often quoted abstract


D-limonene is one of the most common terpenes in nature. It is a major constituent in several citrus oils (orange, lemon, mandarin, lime, and grapefruit). D-limonene is listed in the Code of Federal Regulations as generally recognized as safe (GRAS) for a flavoring agent and can be found in common food items such as fruit juices, soft drinks, baked goods, ice cream, and pudding.

D-limonene is considered to have fairly low toxicity. It has been tested for carcinogenicity in mice and rats. Although initial results showed d-limonene increased the incidence of renal tubular tumors in male rats, female rats and mice in both genders showed no evidence of any tumor. Subsequent studies have determined how these tumors occur and established that d-limonene does not pose a mutagenic, carcinogenic, or nephrotoxic risk to humans. In humans, d-limonene has demonstrated low toxicity after single and repeated dosing for up to one year.

Being an excellent solvent of cholesterol, d-limonene has been used clinically to dissolve cholesterol-containing gallstones. Because of its gastric acid neutralizing effect and its support of normal peristalsis, it has also been used for relief of heartburn. D-limonene has well-established chemopreventive activity against many types of cancers. Evidence from a phase I clinical trial shows a partial response in a patient with breast cancer and stable disease for more than six months in three patients with colorectal cancer. (Altern Med Rev 2007;12(3):259-264)

it’s listed in some references as toxic, and others as non toxic.

D-limonene – This chemical is produced by cold-pressing orange peels. The extracted oil is 90% d-limonene. It is a sensitizer, a neurotoxin, a moderate eye and skin irritant, and can trigger respiratory distress when vapours are inhaled  by some sensitive individuals.  There is some evidence of carcinogenicity.  D-limonene is the active ingredient in some insecticides. It is used as a solvent in many all-purpose cleaning products, especially ‘citrus’ and ‘orange’ cleaners.  Also listed on labels as citrus oil and orange oil.

there’s nothing conclusive on the epa iris site, because they don’t address it.  they’re discussing possible inhalation problems when the only studies they list have been ingestion studies.

try not to ingest more than a drop of orange oil at a time.

The health effects data for d-limonene were reviewed by the U.S. EPA RfD/RfC Work Group and determined to be inadequate for the derivation of an inhalation RfC. The verification status for this chemical is currently NOT VERIFIABLE. For additional information on the health effects of this chemical, interested parties are referred to the documentation listed below.

NOT VERIFIABLE status indicates that the U.S. EPA RfD/RfC Work Group deemed the database at the time of review to be insufficient to derive an inhalation RfC according to the Interim Methods for Development of Inhalation Reference Concentrations (U.S. EPA, 1990). This status does not preclude the use of information in cited references for assessment by others.

d-Limonene (1-methyl-4-isopropenyl-1-cyclohexene) is a liquid with a lemonlike odor. It is a major constituent in several citrus oils (orange, lemon, mandarin, lime, and grapefruit) and is present in a number of other essential oils, as well. d-Limonene is included on the Food and Drug Administration’s (FDA’s) Generally Recognized as Safe List and is approved for use by the FDA as a food additive (Opdyke, 1975). d-Limonene has a boiling point of 176 C and a vapor pressure of <3 mmHg at 14 C. d-Limonene is used primarily as a flavor and fragrance ingredient.

No information is available on the health effects of inhalation exposure to d-limonene in humans, and no long-term inhalation studies have been conducted in laboratory animals. NTP (1990) conducted a series of studies that investigated the toxicity of d-limonene (>99% pure) in both Fischer 344/N rats and B6C3F1 mice.

the  pesticide info site is very mild on the risks from limonene exposure:

Not Listed
Not Listed
Not Available
Slightly Toxic
Not Acutely Toxic to Slightly Toxic

here’s a look at the msds for food-grade d-limonene.  i wouldn’t put the stuff in my eye, that’s for sure.  mucous membranes and orange oil is a very bad idea.  once i lightly ran a freshly dipped q-tip around the outside of my ear canal, and ten minutes later my ear was hot and stinging and i felt like it was going to burn a hole thru to my brain.

so don’t put it in any orifice, okay?  think of it like you would tiger balm.  there are places you just shouldn’t let that stuff get onto.

Emergency Overview
Appearance/Odor: Colorless liquid with citrus aroma.
Product is Combustible.
Slippery when spilled.
Potential Health Effects: See Section 11 for more information.
Likely Routes of Exposure: Eye contact, skin contact, inhalation.
Eye: Causes moderate to severe irritation.
Skin: May cause slight redness. Prolonged or repeated exposure may cause drying of the skin.
Inhalation: May cause nose, throat, and respiratory tract irritation, coughing, headache.
Ingestion: Not likely to be toxic, but may cause vomiting, headache, or other medical problems.
Medical Conditions Aggravated By Exposure: May irritate the skin of people with pre-existing skin conditions.
This product does not contain any carcinogens or potential carcinogens as listed by OSHA, IARC, ACGIH or NTP.
OSHA Regulatory Status
This material is combustible, which is defined as having a flash point between 100oF (37.8oC) and 200oF (93.3oC). Combustible materials are haz-
ardous according to the OSHA Hazard Communication Standard (29 CFR 1910.1200).

there are varying reports about toxicity and sensitization.

d-Limonene is not acutely toxic.
Oral: LD50 >5 g/kg, rabbit
Dermal: LD50 >5 g/kg, rabbit
Skin: The skin irritancy of limonene in guinea pigs and rabbits is considered moderate and low, respectively.
Sensitization: d-Limonene is not a sensitizer. Improper storage and handling can lead to oxidation. The oxidized forms
of d-Limonene have been shown to be a skin sensitizer.
Inhalation: RD50 >1000 ppm
Chronic Toxicity: Not listed as a carcinogen (OSHA, NTP, IARC, or ACGIH)
Ecotoxicological Information: Product may be toxic to aquatic organisms.

a technical book on aromatherapy doesn’t like citrus oil at all once it oxidizes, and warns about skin and lung problems from long term use.  that involves sensitization, for which, again, the evidence is mixed.

so don’t touch it, and use proper ventilation.

the human metabolome project seems to conclude d-limonene isn’t bad for humans, but it’s ard to tell.

The scientific data base demonstrates that the tumorigenic activity of d-limonene in male rats is not relevant to humans. The three major lines of evidence supporting the human safety of d-limonene are (1) the male rat specificity of the nephrotoxicity and carcinogenicity; (2) the pivotal role that alpha 2u-globulin plays in the toxicity, as evidenced by the complete lack of toxicity in other species despite the presence of structurally similar proteins; and (3) the lack of genotoxicity of both d-limonene and d-limonene-1,2-oxide, supporting the concept of a nongenotoxic mechanism, namely, sustained renal cell proliferation. (PMID: 2024047)

evidently citrus oil is being investigated for anti-cancer properties.


D-Limonene is a natural monoterpene with pronounced chemotherapeutic activity and minimal toxicity in preclinical studies.

D-Limonene is well tolerated in cancer patients at doses which may have clinical activity. The favorable toxicity profile supports further clinical evaluation.

here’s a county-level advisory on d-limonene, which they list as an insect repellant.  it’s not mobile, it’s not persistent.  don’t be dumping it in any streams.  otherwise, the safety features go on and on.

Mobility Summary:
D-Limonene is not very soluble in water and it adheres strongly to soil with organic matter. Because d-limonene dissipates quickly into the air and binds
strongly to soil it is not expected to move off the site of application and get into surface water or ground water. The hazard for mobility is rated low.

Persistence Summary:
D-Limonene has a high vapor pressure so it is likely to dissipate into the air when it is applied to vegetation or to the ground. In the air, d-limonene will
react with other chemicals and degrade within minutes to hours. If d-limonene gets into water it will volatilize off the surface, breakdown in sunlight, and
bind to sediments. After d-limonene is introduced to the environment, it is likely to reach half of the applied concentration in less than one week.
Thurston County rates the hazard of chemical persistence as low.

Bioaccumulation Summary:
D-Limonene adheres more readily to organic solvents than to water indicating the potential to bind to fish or animal tissue. Calculated bioconcentration
factors indicate that there is a moderate hazard for accumulation in fish tissue. The hazard for bioaccumulation is rated moderate.

Acute Toxicity Testing and Ecotoxicity Summary:
Single-dose toxicity testing indicates that d-limonene is highly toxic to worms, fish, and other aquatic organisms but low in toxicity to mammals and birds.
It is assumed that it is highly toxic to bees and other insects because it is an active ingredient for insecticides. Toxicity to pets and wildlife is not expected
from the insecticidal use of d-limonene because it dissipates rapidly into the air and contacting treated vegetation or soil is not likely to cause a significant
exposure (except to insects and possibly to worms). Risk of toxicity to non-target organisms from the use of d-limone products is rated low.

i’m looking for specific references to orange oil fumes, because in general, breathing solvent fumes are a very bad idea.  it’s killed at least one old-school encaustic painter – turpentine yek fui.  his name was karl zerbe.

In the 1930s Levine experimented briefly with encaustic, as did Hyman Bloom. Both are commonly associated with Karl Zerbe as leaders of Boston Expressionism who, by 1940, sought to transform nature-based imagery into symbolic representations of deeper expressive content. Although Levine and Bloom did not continue their experiments, Zerbe is commonly credited with almost single-handedly reviving the use of the encaustic medium through his teaching and well-publicized exhibitions of his work during the 1940s.

In 1936, Zerbe came across some incidental references to Fayum portraits and became excited at the possibility of updating the ancient encaustic technique. Finding that there was little published on the subject, he began his own experiments, beginning with a pie pan on a kitchen stove. He proceeded to experiment with various types of waxes, resins, and oils in many combinations and temperatures, even enduring the cracking of some early examples. Zerbe eventually found the right mixture: ninety percent beeswax and ten percent of sun-thickened linseed oil, heated to 225 degrees Fahrenheit on a thermostatically controlled electric palette. For the burning in process, he employed electric heaters, such as diathermic hand-lamps and blow-torches.

In 1949, Zerbe ended a decade of preoccupation with encaustic. His last painting of the era in this medium was Job (1949, Museum of Fine Arts, Boston); the agonized subject is a portrait of Zerbe himself facing a personal crisis. Zerbe was increasingly debilitated by bronchial asthma, aggravated by the turpentine solvent fumes generated by his encaustic process. Nevertheless, Zerbe had already continued to explore other mediums and now turned to experimentation with plastic-based paints, especially polymer tempera, and acrylics — at times reminiscent of his work in encaustic.

In 1955, Zerbe became a Professor of Art at Florida State University in Tallahassee. There he occasionally continued to use encaustic, as evidenced by his painting Church at Dawn of 1956, featured in a movie of Zerbe demonstrating the medium as a “controlled accident” process with unpredictable results that can be selectively enhanced. Right before his death in 1972, Zerbe was trying to develop a “cold wax” encaustic process, as exemplified by his last series of bird paintings which combine that technique with Magna (acrylic resin). At Florida State University, Zerbe was a highly influential teacher for many students, including encaustic painters Nancy Reid Gunn and Robin Rose.

but i’m looking for specific references to this kind of thing happening with heated citrus oil fumes.

but in the meantime, here’s a caution about overheating wax in general, by one of the commercial leaders in the renaissance in encaustic painting.

With adequate ventilation and proper working temperatures (under 220°F) encaustic is safe and non-toxic.  Usually, working next to a window exhaust fan and having a source of fresh air coming in from another part of the studio, gets rid of fumes adequately.  It is important to ventilate, because wax fumes can be irritants, causing headaches, nausea and labored breathing.  Keep in mind, at temperatures over 250°F, the wax fumes become more concentrated and therefore, toxic and flammable.  Warning signs of this are an acrid odor and smoking wax.  For more information on ventilation, see our ventilation technical sheet.

there are various forums that discuss the problem of heating wax for encaustic painting.  there are various opinions, and quite a lot of emotion and insistence.  read the comments.

This summer at one of the workshops at the Encaustic Conference, there was a big debate over encaustic ventilation safety. It’s a hot topic because people have different opinions about the damage that working with encaustic can cause. I’d like to get an idea of what our team members think about this, and hopefully we can all learn a little more about the process.

this herbal handbook indicates that citrus oil – monoterpene – is used in all sorts of medical applications, including pulmonary ones.

These monoterpene compounds are found in nearly all essential oils and have a structure of 10 carbon atoms and at least one double bond. The 10 carbon atoms are derived from two isoprene units. They react readily to air and heat sources. For this reason citrus oils do not last well, since they are high in monoterpene hydrocarbons and have a quick reaction to air, and are readily oxidized. Although some quarters may simply state that these components have anti-inflammatory, antiseptic, antiviral and antibacterial therapeutic properties while some can be analgesic or stimulating with a tonic effect, it could be seen as a very broad generalization, since this large group of chemicals vary greatly. Since some have a stimulating effect on the mucus membranes they are also often used as decongestants.

but i’m not finding anything that says heated citrus oil is a problem.  ventilate properly, is all, and that should be a no-brainer.  especially if you start getting a headache, or nauseated, or a sore throat.  duh.

Solvent fumes themselves are toxic. Pure Turpentine fumes are less toxic than petroleum distillates, white spirits, and some alternative solvents. Always be sure that your workplace is well ventilated.

Smelly solvent such as Turpentine is actually less toxic than the scent-less solvents. Plus, you can smell whether you have adequate ventilation or not.

so i feel pretty confident in recommending citrus oil as a safe alternative to both turpentine and mineral spirits in the studio, and particularly recommend it as the solvent in cold wax preparations.

there are commercial cold wax preparations, chiefly two, gamblin and dorland.

Gamblin Cold Wax Medium is made from naturally white unbleached beeswax, alkyd resin, and odorless mineral spirits (OMS)

there are a good few people experimenting with cold wax, and it’s a very versatile painting medium.  the links in this paragraph in particular go to artists working with cold wax, or discussions about it.

anyway, it’s time to get dinner on.  i’m hungry thinking about citrus oil.  here’s my latest encaustic painting.

baby falls, tellico river. beeswax, orange oil, pigment, river stones


6 thoughts on “how toxic is orange oil?

  1. Thank you for sharing your extensive research! Health & safety is important, and it’s easy to forget as we artists enthusiastically explore new techniques and materials. As we rush headlong, it’s best to be well informed so we don’t experiment with our health!

  2. By the way… it’s no wonder that “Zerbe was increasingly debilitated by bronchial asthma” if the following is true:

    “Zerbe eventually found the right mixture: ninety percent beeswax and ten percent of sun-thickened linseed oil, heated to 225 degrees Fahrenheit on a thermostatically controlled electric palette. For the burning in process, he employed electric heaters, such as diathermic hand-lamps and blow-torches.”

    Yikes! It might have been “right” in that he achieved the look he wanted and the texture was good to paint with, but he didn’t pass out or burn his studio down!

    That’s too hot for beeswax, and linseed oil is highly flammable… supposedly a pile of linseed oil soaked rags can burst into flame. Blow torches are still popular today but I steer clear because of the increased risk of burned wax (very unhealthy fumes).

    I stick to a thermostatically controlled pancake griddle which is plenty hot at around 200 degrees F (some think that’s pushing it), and a heat gun (always moving to avoid overheating).

    Filtered beeswax supposedly starts melting around 170 degrees F. I add 10-15% damar resin (powdered tree sap) to raise the melting point of the wax, so it’s more durable and can polish up nice and shiny (if desired).

    I’ve been doing a few encaustic (melted wax) paintings per year for about 4 yrs now. I love it, but am eager to try cold wax techniques to get a more sensual blended look & paint stroke. Orange oil solvents seem to be the least problematic health wise (at least so far in my research). However, I’d be cautious in EVER heating one of those paintings, as I don’t trust that the solvent ever truly completely goes away. I’d probably have a separate set of solvent brushes that I’d never heat.

    I can see painting cold wax (solvent & wax) over an encaustic painting (melted wax), since cold wax is better for finessed details. But I don’t see the point of doing things the other way around, and wonder if that’s an unstable lean over fat situation, destined for cracking or separating. But I’m sure there’s some people who find some advantage in that approach.

    Thanks again for sharing this useful info!

    Let’s not repeat poor Zerbe’s tragic mistakes!

    • as for fat over lean, i have seen on the amien forum that there is no such thing with wax, so you can do it in any order you like. the important thing is to get the layers to fuse. i haven’t found out scientifically if it’s true, but my suspicion is that the solvent melts the wax and fuses it together in one big orangey lump.

      as for orange oil heated, it’s probably not a great idea to snort it, but i’ve got asthma and have been using it for two or three years now, with no ill effects whatever. if you ventilate your studio, put a fan across the work surface between your nose and the wax, then it’ll probably work fine.

      zerbe was a colleague of walt martin, who was also an encaustic artist. walt used turpentine in his mix, which is a definite poison when inhaled. it made me very sick when i tried it myself, in my early days as an encaustic pioneer. but after my switch to orange oil, i’m not having any of those problems, especially when burning in.

  3. OH… and I love how you creatively incorporated stones into your wax painting, and the lovely fluid water effect!

    Did you really heat that?! Encaustic traditionally means heat fused wax, but I noticed you used orange solvent.

    • yes i heated it. yes i used orange oil solvent. no i did not use hermetic isolation methods while burning in. i heated it to a molten state with an ordinary light bulb. i did not have any problems with heated solvent fumes, because they’re orange oil, and merely make me hungry. i put the rocks down first with molding paste, but i pressed the tiny stones into the hot wax after i was finished. the fluidity of the water comes from letting the wax flow. that’s why i think encaustic’s so well suited to water paintings. i’m doing several with clouds right now, and wax is also just the thing for rendering clouds.

  4. Beautiful painting Jeanne.

    My but you are thorough in your explanations on these H&S issues. Thank you so much.

    When I think about my early days painting…. in the kitchen as I cooked the dinner for the kids! When I started to read about the toxic nature of pigments and such I soon gave that up! I mean moved to a different room.

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