This list contains essential oils that should be avoiding in aromatherapy. If you are new to aromatherapy, it is important to be familiar with the toxic oils as some sellers offer toxic oils without informing newcomers of the dangers.

The list below contains oils that should not be used in aromatherapy without the express administration of a qualified aromatherapy practitioner. Many should not even be used by a qualified practitioner. Do not assume that an oil is safe to use if it is not on this list. Read the safety data on any essential oils you use.

Ajowan - Trachyspermum copticum

Almond, Bitter - Prunus dulcis var. amara

Arnica - Arnica Montana

Birch, Sweet - Betula lenta

Boldo Leaf - Peumus boldus

Broom, Spanish - Spartium junceum

Calamus - Acorus calamus var. angustatus

Camphor - Cinnamomum camphora

Deertongue - Carphephorus odoratissimus

Garlic - Allium sativum

Horseradish - Armoracia rusticana

Jaborandi - Pilocarpus jaborandi

Melilotus - Melilotus officinalis

Mugwort - Artemisia vulgaris

Mustard - Brassica nigra

Onion - Allium cepa

Pennyroyal - Mentha pulegium

Rue - Ruta graveolens

Sassafras - Sassafras albidum

Thuja - Thuja occidentalis

Wintergreen - Gaultheria procumbens

Wormseed - Chenopodium ambrosioides var. anthelminticum

Wormwood - Artemisia absinthium