The essential oils to avoid during pregnancy are those rich in constituents linked to miscarriage, birth defects or fetal toxicity, mostly in animal studies. The best known are aniseed and fennel (anethole), wintergreen and sweet birch (methyl salicylate), wormwood and Dalmatian sage (thujone), pennyroyal (pulegone), parsley seed (apiole) and Spanish lavender (camphor). Most other common oils stay usable, at lower strength.
Check with your midwife or doctor before using any essential oil while pregnant, especially if your pregnancy is high-risk. The usual safety habits still apply, from how to patch test an essential oil to reading an essential oil dilution chart before anything touches your skin. Pregnancy tightens both, because skin can react differently than it did before, and 1% becomes the ceiling for topical blends.
Which essential oils should you avoid during pregnancy?
Leave out every oil on the pregnancy list in Tisserand and Young's Essential Oil Safety (2nd edition, 2014), whether on skin, in the bath or in a diffuser. The table shows the ones US shoppers meet most, with the constituent behind each warning, from a 2021 review by Dosoky and Setzer.
| Oil | Constituent of concern | What the concern is |
|---|---|---|
| Aniseed, star anise, sweet and bitter fennel, aniseed myrtle | (E)-anethole | Estrogenic; reduced embryo implantation in pregnant rats |
| Wintergreen, sweet birch | Methyl salicylate | Crosses the placenta; birth defects in animal studies |
| Cassia, cinnamon bark | Cinnamaldehyde | Embryotoxic in rodent studies |
| Wormwood, Dalmatian sage, thuja, tansy, mugwort, western red cedar | Thujone | Neurotoxic; can cause convulsions |
| Spanish sage, savin | Sabinyl acetate | Embryotoxic and abortifacient in rodents; no safe level established |
| Pennyroyal, buchu, lesser calamint | Pulegone | Breaks down into liver-toxic compounds such as menthofuran |
| Parsley leaf and seed, Indian dill seed | Apiole | Liver and kidney toxicity, and abortion, at high doses in animals |
| Spanish lavender, ho leaf (camphor type), feverfew | Camphor | Crosses the placenta; humans may be more sensitive than test animals |
| Oil | Constituent of concern | What the concern is |
| Myrrh | Beta-elemene, furanodiene | Block the growth of new blood vessels, which pregnancy depends on |
| Black seed essential oil | Thymoquinone | Fetal loss in rat studies; also blocks new blood vessel growth |
| Carrot seed | Whole oil | Stopped embryo implantation in rodent injection studies |
| Oregano | Whole oil (culprit not identified) | Embryotoxic in mice at oral doses |
Rarer oils on the full list include rue, blue cypress, costus, chaste tree, hyssop (pinocamphone type), green yarrow and zedoary.
Which essential oils are considered safe during pregnancy?
Most everyday oils are considered fine in pregnancy at 1% or less. The pregnancy guidelines of the International Federation of Professional Aromatherapists (IFPA), which NAHA endorses, list lavender (Lavandula angustifolia), frankincense, sweet orange, mandarin, lemon, grapefruit, bergamot, neroli, petitgrain, Roman and German chamomile, geranium, ginger, sweet marjoram, sandalwood, cypress, tea tree and ylang ylang.
If you'd rather start from a shortlist, Miracle Botanicals groups its essential oils selected for pregnancy in one collection. Whatever you buy, check the Latin name. "Lavender" can mean camphor-rich Spanish lavender (Lavandula stoechas), and "sage" can mean thujone-rich Salvia officinalis. The GC/MS report shows the camphor or thujone percentage, and Miracle Botanicals posts one on the product page of every single oil, as its FAQ on GC/MS test reports explains.
A few oils on that list need extra care. IFPA notes that chamomile and tea tree can irritate or sensitize skin. Cold-pressed citrus oils add sun risk, and IFPA says raised melanocyte-stimulating hormone makes pregnant women more likely to burn. See phototoxic essential oils for which ones and for how long.
Can you use essential oils in the first trimester?
The cautious answer is no topical use in the first trimester (weeks 1-13), and only light inhalation if your midwife agrees. These are the weeks when the baby's organs form, and the rodent data on sabinyl acetate point at this window specifically. NAHA's evidence-based prenatal list starts its earliest pregnancy use after week 10.
Some sources go further. The UK brand Tisserand Aromatherapy advises avoiding essential oils entirely in the first trimester.
Research doesn't settle the question. In a 2014 Iranian trial, 100 women at 6-16 weeks sniffed 2 drops of distilled lemon oil on a cotton ball whenever they felt nauseous. Their nausea and vomiting scores were lower than the placebo group's on days 2 and 4 of the 4-day study, not on every day. One small, short trial doesn't show that lemon treats morning sickness, and it measured nothing about the baby.
How much should you dilute essential oils while pregnant?
Keep anything that goes on skin at 1% or lower: 3 drops of essential oil per 10 ml of carrier oil, or 9 drops per 30 ml (1 fl oz). That's the IFPA ceiling for all skin use in pregnancy. Tisserand Institute staff have suggested staying below 2%. Use the lower figure.
| Carrier oil | 0.5% | 1% (maximum) |
|---|---|---|
| 10 ml (1/3 fl oz) | 1 drop | 3 drops |
| 30 ml (1 fl oz) | 4 drops | 9 drops |
| 60 ml (2 fl oz) | 9 drops | 18 drops |
Drop counts use the Tisserand standard of 30 drops = 1 ml and round down. For a bath, IFPA sets a limit of 4 drops in total. Stir them into a tablespoon of carrier oil first, because essential oil doesn't disperse in water. Skip undiluted use completely; the reasons are in our guide to applying essential oils neat.
Oils with a ceiling below 1%
Tisserand and Young set lower pregnancy limits for oils rich in citral, which caused embryo and fetal toxicity in rats given 60 mg/kg a day or more by mouth. The limits are lemongrass and lemon myrtle 0.7%, may chang and lemon tea tree 0.8%, and melissa and lemon verbena 0.9%. In a 10 ml bottle, that means no more than 2 drops of any of them.
Breastfeeding has its own considerations and isn't covered here.
Can you diffuse essential oils while pregnant?
Yes, with oils that aren't on the avoid list, in a ventilated room, and in short sessions. The Tisserand Institute recommends intermittent diffusion of 30-60 minutes on, then 30-60 minutes off, and calls barely noticeable low-level diffusion fine for longer. In pregnancy, stay at the faint end, since your sense of smell is likely sharper.
IFPA notes a heightened sense of smell throughout pregnancy, so a scent you liked last year can bring on nausea now. Turn the diffuser off at the first headache or queasy feeling. A diffuser doesn't make an avoid-list oil acceptable either, so wintergreen and pennyroyal stay on the shelf. France's health safety agency, ANSES, goes further and advised in April 2020 that pregnant women not use essential oils at all.
For water-to-oil ratios by tank size, see how many drops of essential oil in a diffuser, then use the low end.
Is clary sage safe during pregnancy?
The sources disagree, so the conservative answer is to leave clary sage out until labor, and use it then only if your midwife or doctor agrees. Clary sage (Salvia sclarea) isn't on Tisserand and Young's pregnancy list, and IFPA lists it as usable when diluted. Its reputation for stimulating contractions still keeps other sources cautious.
NAHA's clary sage page calls that reputation anecdotal and mentions a NAHA-supported randomized trial by Franklin Health Research set up to test it. NAHA's evidence-based list places clary sage under labor and delivery, not under pregnancy. Tisserand Aromatherapy says clary sage isn't recommended during pregnancy.
Don't use clary sage to try to start labor at home. And check the Latin name: clary sage is a different plant from Dalmatian (common) sage and Spanish sage, both on the avoid list.
How strong is the evidence behind these warnings?
Thin, and mostly from animals. Dosoky and Setzer's 2021 review notes the lack of clinical evidence on reproductive toxicity in humans and leans on rodent studies, many using oral or injected doses far above aromatherapy amounts. It also found no decisive evidence that these oils cause miscarriage at aromatherapy levels.
Documented harm in people comes from a different situation: NAHA cites Ron Guba's point that pregnancy toxicity has involved women swallowing large doses of pennyroyal or parsley seed oil to end a pregnancy. So why avoid the list at all? Nobody has shown those oils are safe for a developing baby, and with about two dozen well-tolerated oils to choose from, leaving the flagged ones out costs you nothing.
The sources also disagree at the edges. IFPA advises against phenol-rich oils in pregnancy, including clove, oregano and thyme (thymol type), because they can irritate skin, yet Tisserand and Young don't list clove. Older bans on lavender and juniper went the other way, and IFPA now calls them outdated. Where reputable sources split, take the cautious side and ask your midwife.
What's the one rule to remember?
If an oil is in the avoid table, keep it out of every method, skin, bath and diffuser, for the whole pregnancy. For everything else, wait out the first trimester, mix no more than 3 drops per 10 ml, and run each new oil past your midwife or doctor before you open the bottle.
