Mint and Tansy to Repel Mice
Answered by: Conrad Richter
Question from: Kathy
Posted on: April 26, 2002

I have found a few references to mint and tansy being used to repel mice because they don’t like the smell. Do you know if this is correct and if so, what kind of mint and tansy would be best? Are either of these herbs harmful to children if ingested or could they cause allergy problems for asthmatics? Also, can they be grown year round indoors?

We have not heard that mint and tansy are effective repellents for mice. We would appreciate receiving a list of references you found so we can share the same information with visitors to our website.

Both tansy and mint are aromatic because they are rich in essential oils and other oleoresins. These oils are released into the atmosphere, particularly after contact with the plants. It is certainly possible that mice find these oils offensive and may just move on when other, less offensive, alternatives are available.

Mint is very safe for children, adults and animals. It has been used in teas, foods, and household products for centuries, so we can be very confident that it is safe. Of course, there is always the possibility that a child will develop a sensitivity or allergy to mint, but that can happen with any substance the child comes in contact with. Certainly, we can say that mint is among the least likely herbs to be a problem for children.

Tansy is known to be allergenic for some sensitive individuals. It is not a widespread phenomenon, but it is something to watch for. It can cause all of the classic allergic reactions: trouble breathing, itchy skin, or skin rash.

For a list of plants known to cause dermatitis, including allergic contact dermatitis, see http://www.lni.wa.gov/sharp/derm/phytoderm.pdf. Tansy is listed. So are peppermint and spearmint; but as already discussed these are very safe herbs but even they can cause allergic reactions in some sensitive individuals. They are certainly not in the same league as poison ivy or poison oak which are much nastier and are listed as causing allergic contact dermatitis also. The list does not differentiate between those plants that are minor risks and those that as major risks.

We do not have information on whether tansy causes respiratory allergies. There is one report (Arch Dermatol 1987 Apr;123:500-2; http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3827282&dopt=Abstract) that looked at whether the allergen route was respiratory or skin contact in the case of a nine year old child who regularly developed rashes on his hands and face in the summer. Because he never developed the rashes on his feet and the rashes went away when contact with the plant was avoided, it was concluded that the allergen route was direct skin contact. It remains, though, that there is still the possibility that breathing in tansy pollen could cause allergies in sensitive individuals and it should be watched. Keeping the plants from blooming will eliminate any risk of pollen.

Both tansy and mint can be grown indoors. It is never easy to grow herbs indoors, particularly sun loving ones, but these are probably among the easiest. Whether they would have any effect on mice is another matter. Even if mice are repelled by these plants, it does not follow that by merely growing the plants in the window will cause mice to go away. Likely, it will be necessary to cut fresh leaves and place them in areas frequented by mice from time-to-time.

There are many varieties of mint. They would not be expected to have the same effects on mice (if any) because the various mints have very different oil compositions. You may wish to experiment with peppermint and perhaps pennyroyal – two mints that have strong odours. Of tansy, you should stick with the common variety, Tanacetum vulgare.

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