Is Limonene Safe For Your Skin? Yes!

Posted by Dr. Natasha Ryz on

Limonene is a terpene found naturally in citrus peel.

Pure limonene is safe for most people to use, when it is properly diluted.

However, oxidized limonene (old limonene) may cause irritation in some people with dermatitis.

Limonene is a weak skin sensitizer, and labelled by some as a "worst ingredient" for skin.

But is limonene actually bad for your skin? Should you avoid limonene in skincare?

This article will cover:

  • What is limonene?
  • Why is limonene used in skincare?
  • Is limonene safe?
  • What is oxidized limonene?
  • Sensitizing potential of pure limonene
  • Sensitizing potential of oxidized limonene
  • How to store limonene to prevent oxidation
  • How to formulate skincare safely with limonene
  • Who should avoid limonene?
  • Summary
  • References

What is limonene?

Limonene is a terpene found naturally in citrus peel.

Limonene is a naturally occurring compound found mainly in the skin of citrus fruits, including orange, lemon, lime and grapefruit. 

Limonene is a cyclic monoterpene with the molecular formula C10H16

Limonene has 3 isomers:

  1. D-limonene (also known as (R)-limonene, (+)-limonene) is found abundantly in citrus fruits.
  2. L-limonene (also known as (S)-limonene, (−)-limonene) is found in pine needles and cones.
  3. DL-limonene (also called dipentene) is a mixture of D-limonene and L-limonene.

These isomers are found in different amounts and ratios in various plants. The predominant form of limonene is D-limonene, which is present in nearly 98% of all citrus oils (Bråred Christensson et al., 2009).

D-limonene is the main constituent of cold-pressed essential peel oils from citrus fruits, including tangerine, sweet orange, bitter orange, grapefruit, mandarin, lemon, lime and bergamot. 

Sweet orange essential oil contains ~ 95% limonene.

Why is limonene used in skincare?

Limonene is widely used in skincare products for:

1. Aroma

Limonene is used for its fresh, pleasant citrus aroma. However, the purer the limonene is, the less odor it has (Chiralt et al, 2002; Sell et al, 2004; Kvittingen et al, 2021). 

Commercially, D-limonene is isolated from orange peel. The cruder the D-limonene is, the more impurities it contains, and the more it will smell like orange (Kvittingen et al, 2021). 

2. Cleansing activity

Limonene is used as a cleanser and a degreaser. Limonene is used as a solvent in water-free hand-cleansers at a concentration of about 10% (Karlberg et al, 1997).

    3. Antioxidant activity

    Limonene has antioxidant activity (Anandakumar et al, 2021) and may increase product shelf life. For instance, limonene has been shown to inhibit lipid oxidation, and is being investigated to extend shelf-life in food products (reviewed by Bora et al, 2020).

    Learn more: Why is Limonene used in Skincare?

      4. Permeation enhancer

      Limonene is a permeation enhancer (Mendanha et al, 2017) and can boost absorption of nutrients and active ingredients (Valgimigli et al, 2012).

      Read more: Limonene is a Permeation Enhancer and Boosts Skin Absorption of Vitamins

        Is limonene safe?

        Limonene is considered to have low toxicity (reviewed by Sun, 2007) and is recognized as a safe ingredient for skincare under the current regulatory guidelines for cosmetics (reviewed by Kim et al, 2013). 

        In the USA, the FDA considers limonene as GRAS (generally recognized as safe) when used as a food additive or flavoring, and as a fragrance additive.

        In Europe, limonene is classified as a potential skin sensitizer. This means that it has the potential to cause a temporary skin reaction (such as red, bumpy, or itchy skin) in some individuals. The pure compound limonene can also be broken down to oxidized limonene, e.g. limonene hydroperoxides, which are potential allergens in sensitive individuals (Topham et al, 2003). 

        There is no max dermal limit for limonene, but the EU Cosmetics Regulations require companies to declare if limonene is present at more than 0.001% in a leave-on or 0.01% in a rinse-off product.

        What is oxidized limonene?

        Typically, limonene has a shelf-life of 1 year.

        Limonene becomes oxidized limonene when it is exposed to oxygen in the air. This process happens naturally over time, but occurs faster when limonene is improperly processed or stored.

        When limonene is exposed to oxygen, it breaks down into hydroperoxides called limonene-1-hydroperoxide and limonene-2-hydroperoxide, which are both strong contact allergens (de Groot, 2019).

        Limonene-1-hydroperoxide is a strong sensitizer (Bråred Christensson et al, 2008) and a clinically important allergen (Bråred Christensson et al, 2014).

        There is potential for skin sensitization to occur when skin is repeatedly exposed to limonene break down products.

        To induce oxidized limonene in a lab setting, limonene preparations are exposed to air in an open flask and stirred multiple times a day for 2 months (Karlberg et al, 1991; Karlberg et al, 1992). This procedure was developed in order to mimic industrial handling of limonene when used as solvent (e.g. in paints or as degreasing agent for metal workers), but later it was also applied to various terpenes as a routine test for oxidation (Kern et al, 2014).

        While this 'worst-case scenario' is useful to evaluate and compare the potential of different terpenes and essential oils to spontaneously oxidize, it is not directly relevant to how limonene is stored or used in consumer products or skincare products (Kern et al, 2014).

        For instance, during storage, limonene can be protected from oxidation by several factors, including protection from light, heat and oxygen exposure. 

        In consumer products, limonene is used in a diluted form and mixed with other ingredients, including antioxidants. In addition, consumer products that contain limonene are often sold in closed containers, with limited air contact (Kern et al, 2014). 

        Indeed, the stability of limonene in fine fragrances was tested, and the data indicate that limonene was stable over a 9-month period, with no accumulation of oxidation products (Kern et al, 2014). 

        Sensitizing potential of pure limonene

        The pure compound limonene is a weak sensitizer (Karlberg et al, 1991; Karlberg et al, 1992), and pure limonene rarely causes positive patch test reactions (Santucci et al, 1987; Matura et al, 2005; Schnuch et al, 2007).

        In 10 studies in which pure limonene (non-oxidized) was routinely patch tested at 1%, 2%, 3%, or 10% during 1977–2017, frequencies of sensitization ranged from 0% to 1.6%, but 9 of 10 scored 0.7% or lower (reviewed by Matura et al, 2002; de Groot et al, 2019).

        No positive skin reactions were observed when testing 2% pure D-limonene in 1200 patients with contact dermatitis (Santucci et al, 1987).

        No positive skin reactions were observed when testing 2% pure D-limonene in 320 patients with eczema, who were suspected of having contact allergy to fragrances (van Oosten et al, 2009). 

        No positive skin reactions were observed when testing 20% pure D-limonene in 20 dermatitis patients (Brared Christensson et al, 2009). 

        High concentrations of limonene may be a dermal irritant for some individuals (Falk et al, 1991, York et al, 1995, Topham et al, 2003). 

        Irritant contact dermatitis among workers in citrus fruit canning industries has been reported (Beerman et al, 1938; Schwartz et al, 1938; Birmingham et al, 1951). 

        To reduce the risk of irritation, limonene should always be properly diluted before use on skin.  

        Sensitizing potential of oxidized limonene

        Oxidized D-limonene has been tested in several multicenter studies.

        At 2 European centers, between 1991 and 1995, there were 2800 consecutive patients with dermatitis that were tested with 2%, 3% or 5% D-limonene that was air-oxidized for 10 or 20 weeks. Altogether, 32 out of 1318 (2.4%) patients reacted to any of the test preparations of D-limonene used at the Stockholm test center, while only 17 out of 1482 (1.1%) patients reacted at the Leuven test center (Karlberg et al, 1997).

        Patients were also tested with 0.5% or 1% limonene-hydroperoxides. Altogether, 19 out of 685 (2.8%) patients reacted to the hydroperoxide fraction in the Stockholm population. Only the 0.5% limonene-hydroperoxide fraction was tested in Leuven, with 4 out of 869 (0.9%) testing positive (Karlberg et al, 1997).

        In another multicenter study in Europe in 2002, a total of 2273 patients with dermatitis were tested using 3% oxidized limonene, and 2.8% patients showed positive patch test reactions (Matura, 2002).

        In 2009, a total of 2900 consecutive dermatitis patients were evaluated in 9 centers in Copenhagen, Malmo, Odense, Barcelona, London, Singapore, Melbourne, Seville and Gothenburg. The overall prevalence of positive reactions to 3% oxidized limonene was 5.2%, ranging from 2.3% to 12.1% in the individual centers (Bråred Christensson et al, 2013).

        These studies led to the development of standardized patch test materials of oxidized limonene 3%, with a standardized content of limonene hydroperoxides at 0.3% (hydroperoxides of Limonene 0.3% pet.®) which are manufactured by Chemotechnique Diagnostics AB, Vellinge, Sweden (Ogueta et al, 2021).

        In subsequent multicenter and single-center studies, patch testing with limonene hydroperoxides at 0.3% has shown positive patch test reactions in 1.2% to 9.4% of cases (reviewed by Ogueta et al, 2021).

        How to store limonene to prevent oxidation

        Temperature, light, and oxygen availability are recognized to have a crucial impact on essential oil integrity (reviewed by Turek et al, 2013).

        During storage, limonene can be protected from oxidation by several factors, including protection from light, heat and oxygen exposure.  

        To avoid oxidation of d-limonene, citrus oils should be stored in a dark air-tight container and placed at 4◦C (Karlberg et al, 1994; Tisserand et al, 2014).

        Cold and dark storage of d-limonene in closed vessels has been shown to prevent auto-oxidation for 1 year without addition of anti-oxidant (Karlberg et al, 1994).

        However, adding antioxidants to limonene is recommended (Karlberg et al, 1994; Tisserand et al, 2014). 

        How to formulate skincare safely with limonene

        To reduce the risk of irritation, old, or expired limonene should be avoided.

        Limonene should always be properly diluted when used for skincare, with safety ranges suggested between 0.1 - 3%. Limonene should never form more than 5% of the final cosmetic product, as this increases the risk of potential irritation.

        Skincare products should be packaged in closed containers with pump lids to minimize air contact. 

        Who should avoid limonene?

        People who are sensitive or allergic to limonene should avoid limonene and citrus essential oils. 

        People who have a disturbed or damaged skin barrier should avoid limonene or use limonene with caution, especially with leave-on products.

        Summary

        Pure limonene is safe for most people to use, when it is properly diluted. 

        Oxidized limonene may cause irritation in people with dermatitis or other skin issues. 

        Always choose fresh products, and avoid the use of old or expired products that contain limonene.

        References

        Anandakumar P, Kamaraj S, Vanitha MK. D-limonene: A multifunctional compound with potent therapeutic effects. J Food Biochem. 2021 Jan;45(1):e13566. 

        Beerman H, Fonde´ G H, Callaway J L. Citrus fruit dermatoses. Arch Derm Syph 1938: 37: 225–234.

        Birmingham D J, Campbell P CJr, Doyle H N, McDonald J M. Investigation of occupational dermatoses in the citrus fruit canning industry. A M A Arch Ind Hyg Occup Med 1951: 3: 57–63.

        Bora H, Kamle M, Mahato DK, Tiwari P, Kumar P. Citrus Essential Oils (CEOs) and Their Applications in Food: An Overview. Plants (Basel). 2020 Mar 11;9(3):357.

        Bråred Christensson J, Johansson S, Hagvall L, et al. Limonene hydroperoxide analogues differ in allergenic activity. Contact Dermatitis 2008;59:344–352.

        Bråred Christensson J, Hellsén S, Börje A, et al. Limonene hydroperoxide analogues show specific patch test reactions. Contact Dermatitis 2014;70: 291–299

        Bråred Christensson, J. B., Forsstrom, P., Wennberg, A. M., Karlberg, A. T., and Matura, M. 2009. Air oxidation increases skin irritation from fragrance terpenes. Contact Dermatitis 60: 32–40.

        Chiralt, A.Martínez-Monzó, J.Cháfer, T.Fito, P. Limonene from Citrus. In Functional Foods, Biochemical and Processing AspectsShi, J.Mazza, G.Le Maguer, M., Eds.; CRC PressBoca Raton, FL2002; Vol. 2, pp 169– 187.

        de Groot A. Limonene Hydroperoxides. Dermatitis. 2019 Nov/Dec;30(6):331-335.

        Deza G, García-Bravo B, Silvestre JF, Pastor-Nieto MA, González-Pérez R, Heras-Mendaza F, Mercader P, Fernández-Redondo V, Niklasson B, Giménez-Arnau AM; GEIDAC. Contact sensitization to limonene and linalool hydroperoxides in Spain: a GEIDAC* prospective study. Contact Dermatitis. 2017;76(2):74-80.

        Falk A, Fischer T, Hagberg M. Purpuric rash caused by dermal exposure to d-limonene. Contact Dermatitis.1991 Sep;25(3):198-9.

        Health Canada. Aromatherapy - Essential Oils. December 8, 2015. Available: Ingredient Search (hc-sc.gc.ca). Accessed. February 11, 2022.

        Karlberg AT, Boman A, Melin B. Animal experiments on the allergenicity of D-limonene—the citrus solvent. Ann Occup Hyg 1991;35:419–426.

        Karlberg AT, Magnusson K, Nilsson U. Air oxidation of D-limonene (the citrus solvent) creates potent allergens. Contact Dermatitis 1992;26:332–340.

        Karlberg AT, Magnusson K, Nilsson U. Influence of an anti-oxidant on the formation of allergenic compounds during auto-oxidation of d-limonene. Ann Occup Hyg. 1994 Apr;38(2):199-207.

        Karlberg AT, Dooms-Goossens A. Contact allergy to oxidized d-limonene among dermatitis patients. Contact Dermatitis. 1997 Apr;36(4):201-6.

        Kim YW, Kim MJ, Chung BY, Bang du Y, Lim SK, Choi SM, Lim DS, Cho MC, Yoon K, Kim HS, Kim KB, Kim YS, Kwack SJ, Lee BM. Safety evaluation and risk assessment of d-Limonene. J Toxicol Environ Health B Crit Rev. 2013;16(1):17-38. 

        Kern S, Granier T, Dkhil H, Haupt T, Ellisd G, Natsch A. Stability of limonene and monitoring of a hydroperoxide in fragranced products. Flavour Fragr. J. 2014, 29, 277–286.

        Kvittingen L, Sjursnes BJ, Schmid R. Limonene in Citrus: A String of Unchecked Literature Citings? J. Chem. Educ. 2021, 98, 11, 3600–3607.

        Matura M, Goossens A, Bordalo O, Garcia-Bravo B, Magnusson K, Wrangsjö K, Karlberg AT. Oxidized citrus oil (R-limonene): a frequent skin sensitizer in Europe. J Am Acad Dermatol 2002;47:709–714. 

        Matura M, Sko¨ld M, Bo¨rje A et al. Selected oxidized fragrance terpenes are common contact allergens. Contact Dermatitis 2005: 52: 320–328.

        Mendanha SA, Marquezin CA, Ito AS, Alonso A. Effects of nerolidol and limonene on stratum corneum membranes: A probe EPR and fluorescence spectroscopy study. Int J Pharm. 2017 Oct 30;532(1):547-554.

        Natsch A, Nägelin M, Leijs H, van Strien M, Giménez-Arnau E, Vey M, González C. Exposure source for skin sensitizing hydroperoxides of limonene and linalool remains elusive: An analytical market surveillance. Food Chem Toxicol. 2019 May;127:156-162. 

        Ogueta IA, Christensson JB, Giménez-Arnau E, Brans R, Wilkinson M, Stingeni L, Foti C, Aerts O, Svedman C, Gonçalo M, Giménez-Arnau A. Limonene and linalool hydroperoxides review: pros and cons for routine patch testing. Contact Dermatitis. 2022 Feb 4. 

        Ravichandran C., Badgujar P.C., Gundev P., Upadhyay A. Review of toxicological assessment of d-limonene, a food and cosmetics additive. Food Chem. Toxicol. 2018;120:668–680.

        Santucci B, Cristaudo A, Cannistraci C, Picardo M. Contact dermatitis to fragrances. Contact Dermatitis 1987: 16: 93–95; 4.

        Schnuch A, Uter W, Geier J, Lessmann H Frosch PJ. Sensitization to 26 fragrances to be labelled according to current European regulation. Results of the IVDK and review of the literature. Contact Dermatitis. 2007 Jul;57(1):1-10.

        Schwartz L. Cutaneous hazards in the citrus fruit industry. Arch Dermatol 1938: 37: 631–649.

        Sell, C. S. Scent through the Looking GlassChem. Biodiversity 200411899– 1920.

        Sharmeen JB, Mahomoodally FM, Zengin G, Maggi F. Essential Oils as Natural Sources of Fragrance Compounds for Cosmetics and Cosmeceuticals. Molecules. 2021 Jan 27;26(3):666. 

        Sun J. D-Limonene: safety and clinical applications. Altern Med Rev. 2007 Sep;12(3):259-64.

        Tisserand, R.; Young, R. Essential Oil Safety, 2nd ed.; Elsevier: New York, NY, USA, 2014.

        Topham EJ, Wakelin SH. D-Limonene contact dermatitis from hand cleansers. Contact Dermatitis. 2003 Aug;49(2):108-9. 

        Turek C, Stintzing FC. Stability of Essential Oils: A Review. Comprehensive Reviews in Food Science and Food Safety. 2013 Jan;3:40-53.

        van Oosten EJ, Schuttelaar ML, Coenraads PJ. Clinical relevance of positive patch test reactions to the 26 EU-labelled fragrances. Contact Dermatitis. 2009 Oct;61(4):217-23. 

        Valgimigli L, Gabbanini S, Berlini E, Lucchi E, Beltramini C, Bertarelli YL. Lemon (Citrus limon, Burm.f.) essential oil enhances the trans-epidermal release of lipid-(A, E) and water-(B6, C) soluble vitamins from topical emulsions in reconstructed human epidermis. Int J Cosmet Sci. 2012 Aug;34(4):347-56.

        York M, Basketter DA, Cuthbert JA, Neilson L. Skin irritation testing in man for hazard assessment - evaluation of four patch systems. Hum Exp Toxicol. 1995 Sep;14(9):729-34.

         

        Aroma Essential Oil Safety Essential Oils Limonene Natural Ingredients Terpenes

        ← Older Post Newer Post →



        Leave a comment