A Google search for “Avoid high doses of lavender oil during pregnancy because it is a uterine stimulant” produces about 10,500 hits, though none of these will tell you how much constitutes a “high dose”. (Yes, I checked every single one.) Other Google search results about lavender in pregnancy include:
“Lavender oil is a uterine stimulant” – 15,800 hits.
“Lavender is an emmenagogue” – 106,000 hits.
“Lavender should be avoided in the first trimester” – 191,000 hits.
Clearly there is some concern about the safety of lavender oil during pregnancy, although there are also a number of sites where lavender is either absent from “should not be used in pregnancy” lists – in fact it is only rarely found on such lists – or where the oil is actually stated to be safe in pregnancy.
The safety concerns raise questions such as:
- Is lavender oil a menstrual stimulant?
- Is lavender oil a uterine stimulant?
- If it is either or both of these, what is the dose threshold?
- Is lavender oil safe to use in pregnancy?
Particular risks that would apply to the first trimester are (a) an increased risk of miscarriage and (b) risk of fetal malformation. However, these risks do not go away after three months, and so limiting avoidance of a reproductively toxic substance to the first trimester only makes sense if there is evidence to support this guideline. But, is lavender oil even reproductively toxic at all?
An emmenagogue, or menstrual stimulant, may act by directly stimulating uterine contractions, or through stimulating hormone production. Bartram (1995) defines emmenagogues as: “Plant substitutes for hormones that stimulate the pituitary gland to produce more gonadotrophic hormones. Herbs that initiate and promote the menstrual flow. Most are uterine tonics and stimulants to restore normal function of the female reproductive system. Not used in pregnancy, except when a practitioner has good cause to do so in the first few weeks.” Bartram goes on to list 54 herbs, though lavender is not one of them.
The absence of lavender from Bartram’s list is not surprising since it has not traditionally been regarded as a herb to avoid in pregnancy, or as a uterine stimulant. Culpeper (1652) did say that “lavender….provokes women’s courses”, i.e. stimulates menstruation, but he was referring to spike lavender, not true lavender. In his 1964 text, Dr. Jean Valnet refers to lavender oil as an emmenagogue when internally used, though he gives no contraindication for pregnancy. Lawless (1992) also cites lavender oil as an emmenagogue, though not limited to internal use, and there is similarly no pregnancy contraindication. Franchomme and Pénöel (1990) give no contraindications at all for lavender oil, and do not mention menstrual stimulation but they do list an antispasmodic action for the oil. An antispasmodic action on the uterus suggests a substance that is helpful in menstrual pain, and not one that would stimulate menstruation.
Davis (1999) says that lavender oil is helpful in “reducing…scanty menstruation” and that it should be avoided during the first trimester. It seems likely that Davis was picking up on Valnet’s use of “emmenagogue” and that her mention of first trimester avoidance was an assumption on her part. Tiran (2000) mentions that lavender oil “contains a small amount of the ketone camphor, which can be emmenagogic” and that it “should be used with caution in early pregnancy”. In fact the amount of camphor in true lavender oil is very small and camphor only presents a risk in pregnancy in massive doses (see below).
Herbal safety texts
Three herbal safety texts have concluded that lavender flowers are safe to use in pregnancy, and one of theses includes the essential oil. (These are the only such texts in my possession – there may be others that draw different conclusions.) McGuffin et al (1997) give lavender flowers a “Class 1” rating, meaning generally safe to use, with no contraindication for pregnancy or breastfeeding. They apply this to Lavandula angustifolia (true lavender) L. latifolia (spike lavender), L. stoechas (Spanish lavender) and L. x intermedia (lavandin). Mills and Bone (2005) state that using lavender flowers (L. angustifolia and L. spica) is compatible with breastfeeding, and is safe in pregnancy: “No increase in frequency of malformation or other harmful effects on the foetus from limited use in women.”
The Complete German Commission E Monograph for lavender lists L. angustifolia, both flowers and essential oil, as officially “approved” and with no side effects and no contraindications. This includes internal use of 1-4 drops (20-80 mg) of the essential oil as a daily dose (Blumenthal et al 1998). The Commission E Monographs are generally regarded as the most authoritative source on the safety of herbal medicines.
What the research shows
Camphor is neither reproductively toxic nor abortifacient except in almost fatal doses, and a lethal human dose is approximately 200 mg/kg. No adverse fetal effects were seen from feeding camphor to pregnant rats at 1,000 mg/kg/day, or pregnant rabbits at 681 mg/kg/day (Leuschner 1997). This non-fetotoxic rabbit dose is equivalent to an adult human dose of 48 g (1.6 oz), and a person would have to ingest 24 kg (52.9 lb) of lavender oil to reach that amount of camphor. Therefore the camphor in lavender oil presents no risk.
Linalool is not reproductively toxic. When it was administered by stomach tube to pregnant rats at 250, 500 or 1,000 mg/kg/day, on gestational days 7-17, no fetal toxicity or teratogenicity occurred at any dose level (Politano et al 2008). The high dose is equivalent to an adult human ingesting 70 g of linalool, or approximately 200 g (7 oz) of lavender oil. Linalyl acetate has not been tested on animals for reproductive toxicity.
The research shows that lavender oil (L. angustifolia) is not a uterine stimulant. When used on the isolated rat uterus, it in fact reduced contractions (Lis Balchin and Hart 1999). And, lavender oil has no apparent adverse effects during childbirth. It was one of ten essential oils offered to 8,058 women in an 8-year study at the John Radcliffe Hospital in Oxford, UK. Aromatherapy did, however, reduce the need for pain medication. During the years of the study, the use of pethidine in the study center declined from 6% to 0.2% of women (Burns et al 2000).
One in vitro study found that lavender oil had a very weak estrogenic action in MCF-7 breast cancer cells (Henley et al 2007). However, there is no evidence that lavender oil has any adverse effects on human hormonal activity. In another in vitro study, lavender oil inhibited the growth of MCF-7 cells (Zu et al 2010) suggesting that, while it may bind to estrogen receptor sites in the body, it is not an estrogen mimic, and so does not promote estrogen.
Proving safety in pregnancy is always a challenge, but all the indications are that lavender oil is completely safe to use. It is certainly not a uterine stimulant – in any dose. The online references to lavender oil as a uterine stimulant presumably originated from the few books (probably beginning with Valnet in 1964) that describe it as having an emmenagogic action. An assumption was then made that this was due to a uterine stimulant effect, and a further assumption was made that therefore lavender oil could pose a risk of miscarriage in pregnancy. However, there is no evidence that either lavender flowers or lavender oil stimulate menstruation. Thus are myths conceived. Patricia Davis, I’m sure, felt her caution was well-founded, but with the benefit of hindsight we can see that it was an over-reaction. Erring too heavily on the side of safety has a downside – it creates fear, doubt and confusion.
Finally…while searching the internet for the alleged dangers of lavender oil in pregnancy, I came across this advice on a Vitamins and Health Supplements Guide page: “Pregnant and breastfeeding women should avoid using lavender, as it is a uterine stimulant.” What, breastfeeding women too? The logic of this escapes me. Surely a woman wants her uterus to contract back to it’s normal size after childbirth. (Not that lavender oil would do this anyway.)
Bartram T 1995 Encyclopedia of herbal medicine. Grace Publishers, Christchurch UK, p166
Blumenthal M, Busse WR, Goldberg A et al 1998 The complete German Commission E monographs: therapeutic guide to herbal medicines. American Botanical Council, Austin, Texas, p160
Burns EE, Blamey C, Ersser SJ et al 2000 An investigation into the use of aromatherapy in intrapartum midwifery practice. Journal of Alternative & Complementary Medicine 6:141-147
Culpeper N 1652 The English Physitian, or an Astro-physical discourse of the vulgar herbs of this nation. Being a compleat method of physick, whereby a man may preserve his body in health; or cure himself, being sick. Thomas Kelly, London
Davis P 1999 Aromatherapy an A-Z. CW Daniel, Saffrom Walden, p322
Franchomme P, Pénöel D 1990 L’aromathérapie exactement. Jollois, Limoges, p364
Henley DV, Lipson N, Korach KS, Bloch CA 2007 Prebubertal gynecomastia linked to lavender and tea tree oils. New England Journal of Medicine 365(5): 479-485
Lawless J 1992 The encyclopaedia of essential oils. Element, Shaftsbury, p118
Lis-Balchin M, Hart S 1999 Studies on the mode of action of the essential oil of lavender (Lavandula angustifolia P. Miller). Phytotherapy Research 13:540-542
McGuffin M, Hobbs C, Upton R et al 1997 Botanical safety handbook. CRC Press, Boca Raton, p68
Mills S, Bone K 2005 The essential guide to herbal safety. Churchill Livingstone, St. Louis, p493
Politano VT, Lewis EM, Hoberman AM et al 2008 Evaluation of the developmental toxicity of linalool in rats. International Journal of Toxicology 27:183-188
Tiran D 2000 Clinical aromatherapy for pregnancy and childbirth. Churchill Livingstone, Edinburgh p137
Valnet J 1964 Aromathérapie. Librairie Maloine, Paris, p225 (English translation: Valnet J 1990 The practice of aromatherapy. CW Daniel, Saffron Walden, p144
Zu Y, Yu H, Fu Y et al 2010 Activities of ten essential oils towards Propionibacterium acnes and PC-3, A-549 and MCF-7 cancer cells. Molecules 15:3200-3210