Adverse Effects of Essential Oils and Herbs

Compiled by

Guardian Angels Pat & Dixie and Mary Jane & Maggie May

It has been noted that in some cases epileptics have been known to seize from exposure to certain scents or botanical extracts, such as essential oils that are used in fragrances or aromatherapy. Studies show that this may or may not be true. Below are examples of the more common essential oils that may be linked to seizure activity, as revealed in some studies. Please note that animals and humans differ in sensitivities, and the reactions to essential oils are unique and unpredictable.


Essential oils and herbs have been used in treating many conditions since ancient times. Aromatic oils have been used for stimulation and relaxation and to aid in the healing process. Some of our epi pups have been helped by the use of Rescue Remedy
made from a blend of the flower essence of Rock Rose, Star of Bethlehem, Impatiens, Cherry Plum, and Clematis. Please note that Rescue Remedy does not contain essential oils, but is essentially the infused "energy" of the plant, and is not harmful to epileptics, nor is an overdose possible, because it is said to heal on a vibrational level instead of a physical one.

However, there is evidence to suggest that some essential oils can initiate seizures. Camphor, eucalyptus, fennel, hyssop, pennyroyal, rosemary, sage, tansy, tea tree (aka: melaleuca), thuja, turpentine, and wormwood are among those oils. Whether it be a trigger brought on by the simple fact that these are pungent oils or that some, such as sage, rosemary, and wormwood, actually contain potent neurotoxins, caution should be used. Again, we are talking about the essential oils. The plant, when used in normal amounts as in cooking, is usually not concentrated in amounts large enough to cause problems.

But please note that all dogs are different and it has been reported that some highly sensitive dogs have had seizure reactions to being near or in contact with these particular garden herbs. Exceptions to this are found in mistletoe, rue, and wormwood. Parts of these plants (leaves, berries) have shown to be toxic in the growing plant.

Animal Nutrition Center, Franklinville, NJ (from web site):

CAUTION: Rosemary - the camphor, thymol and terpineol in Rosemary are highly stimulating. Do not use during pregnancy. Individuals prone to asthma may be bothered by the strong scent and the active ingredients can bring on seizures in epileptics.

There is no sound scientific evidence that any particular essential oils can trigger an epileptic incident. In fact it is well documented that any powerful smell can initiate such an attack. Therefore, the only advice may be avoid the pungent oils like camphor, eucalyptus, tea tree (aka: melaleuca), rosemary, etc. On the other hand, some trials have indicated that the traditionally relaxing oils can substantially reduce the incidence of attacks.


Aromatherapy Magical Garden (from web site):

PRECAUTIONS: Epilepsy: Fennel, hyssop, sage and wormwood (often contained in herbal preparations against parasites) can trigger an attack.

CAUTION: Sage oil contains a toxic component called thujone, which can interfere with the brain and nervous system functions. Sage should not be used by people prone to epileptic seizures.


Elixarome Limited, Kent, England (from web site):

Do not use camphor, fennel, hyssop, rosemary or sage oils if you suffer from epilepsy.

Contains thujone, a neurotoxic ketone, so avoid this oil for anyone prone to seizures.


Life Blends, Dallas, TX (from web site):

The following oils have a powerful action on the nervous system and should be avoided by people with epilepsy:
Fennel, hyssop, rosemary and sage.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~; Elro Company, Palm Coast, Florida:

Description: Thujone is a natural chemical compound found in many different plants and flowers. It is especially known in many spices, herbs, and essential oils. Thujone has a similar chemical structure to Tetrahydrocannibinol (active ingredient found in marijuana or THC) and Menthol (peppermint odor found in many over-the-counter medicated creams).

Can be found in 24 direct food additives according to the FDA's PAFA database.  Dalmation sage oil and cedar leaf oil are stated as containing the highest concentration of thujone. Absinthe, Absente, Vermouth, Benedictine, Elisir du D.R. and Chartreuse contain small amounts of Thujone. This natural chemical is stated to make up 40-90% (by weight) of the essence of wormwood.

Reported side effects of thujone and wormwood are nausea, vomiting, insomnia, restlessness, vertigo, tremors, and seizures. Large doses of thujone have been found to cause delirium, convulsions, seizures, paralysis, brain damage, renal failure and death.


Animal Nutrition Center, Franklinville, NJ - web site
Aromatherapy Magical Garden - web site
Elixarome Limited, Kent, England - web site
Life Blends, Dallas, TX - web site
Prescription for Nutritional Healing, Phyllis A. Balch, CNC, and James F. Balch, MD, 3rd Edition, 2000
Rodale's Illustrated Encyclopedia of Herbs, 1987