- Aniseed
- Birch
- Bitter Almond
- Boldo
- Calamus
- Camphor
- Cassia
- Chenopodium
- Clove
- Crested Lavender
- Garlic
- Goosefoot
- Horseradish
- Hyssop (except decumbens variety)
- Juniper (except Juniper Berry),
- Mugwort
- Mustard
- Oregano
- Pennyroyal
- Red and White Thyme
- Rue
- Santalina
- Sassafras
- Savory
- Tansy
- Terebinth
- Thuja
- Wintergreen
- Wormwood
- Yarrow.
This is not an exhaustive list and there will be other oils out there that are toxic. Always double check and confirm with a vet if in doubt.