Basil, Marjoram and Other Herb Oils: Evidence, Safety and How It Is Used

Safety first. Basil and marjoram oils are for smelling or, as trials used them, for diluted skin application. This page is not advice to swallow any essential oil. Some basil oils are rich in a compound called estragole, which sources describe as a concern in food supplements. [1] For a swallowing accident, call Poison Help at 1-800-222-1222 (US), and 911 for collapse, seizure or trouble breathing.

Which plants, which part, and the name traps

Sweet basil is Ocimum basilicum L. (Lamiaceae) and sweet marjoram is Origanum majorana L. (Lamiaceae); GBIF lists both as accepted. [2] [3] Basil oil is made from basil leaves, according to a 2026 plant-chemistry paper. [4] The marjoram trial summaries we read do not name the plant part.

Do not confuse these with others. Holy basil is a different species, Ocimum tenuiflorum, covered under tulsi. "Oregano" and "marjoram" are related names in the Origanum group, and oregano oil has its own page: oregano oil. Other herb oils have their own pages, for example rosemary oil, thyme oil and lemongrass oil. The plants themselves are covered in basil as an herb.

Why the chemistry of basil matters

"Basil oil" is not one thing. A study of 90 basil lines found five chemotypes (chemical types): linalool, methyl chavicol, citral, methyl cinnamate and methyl eugenol. [4] In one analysis of a basil oil, methyl chavicol made up 86% of the oil. [5] Methyl chavicol is often called estragole. [4]

Estragole in basil-containing food supplements can be converted in the body to a genotoxic and carcinogenic metabolite, according to a laboratory and modeling study. [1] A review lists estragole among compounds found in foods such as herbs and spices. [6] What this means for a bottle of oil used in aromatherapy is not described in the sources we read, so a reader cannot assume that a given oil is low or high in estragole without a label and test report. The label guide is reading an essential oil label.

Traditional use

Traditional use of basil and marjoram oils by named peoples or in named periods is not described in the sources we read, so we do not describe it here. Traditional use would not be proof of benefit either way.

What research shows

All findings below are small studies using self-rated or short-term outcomes. Smell makes real blinding difficult.

The marjoram stress trial is a useful example: the authors' conclusion was positive, but the between-group comparison, which is the fair test, was not significant. [7] See human studies versus lab research.

Proper evidence not found: we searched PubMed for human trials of basil or marjoram oil for sleep, nausea and skin conditions and found nothing we could responsibly summarize here.

Safety

Skin. We did not find basil or marjoram oil named in the skin-allergy sources we read. One review of essential oil allergy says nearly 80 oils have caused contact allergy and most reactions follow pure or high-concentration products. [10] The FDA says many plants contain materials that can irritate or cause allergic reactions on the skin. [11] Both plants are in the Lamiaceae family. Cross-reactions between herbs are covered in herbal allergy and cross-reactivity.

Heart rate. In the marjoram nurse trial, heart rate rose slightly in the marjoram group but stayed in the normal range. [7]

Medicines, pregnancy and breastfeeding, children, liver and kidney, surgery: not described for these oils in the sources we read. That is not proof of safety. Ask a pharmacist or clinician, and see medicine interactions and pregnancy and breastfeeding. Tell a surgical team about oils you use.

Quality. An oil's label should give the botanical name and chemotype; GC-MS testing shows composition, not safety. See quality testing.