Repel Fleas With Pennyroyal

Several years ago I was studying Native American herbalism when I learned about Pennyroyal. As a member of the mint family, Pennyroyal got a bad rap because it has a history of being used to terminate pregnancies, and often had harsh side effects. It has even been known to kill when taken in large doses. But my herbalism teacher told me that Pennyroyal would repel fleas.

So I looked it up. The Latin name for American Pennyroyal is “Hedeoma pulegioides”. Pulegioides looked a lot like the Spanish word for flea – “pulga”. Upon further research I found that first century herbalists wrote of Pennyroyal’s action to repel fleas. They probably knew a little something about how plants worked, so I decided to give it a shot.

Due to its toxicity, I had a difficult time finding pennyroyal for sale. But I was lucky enough to find a patch of pennyroyal growing in a field behind my house (in San Francisco) so I helped myself to a nice-sized cutting.

At the time, I kept my two dogs in a fenced dog run in the back yard while I was at work. So I transplanted my newly discovered Pennyroyal along the edge of the dog’s fence. Within a month, the dogs didn’t seem to need a their regular dose of the chemical flea treatment, so I skipped it. I went another two years without having to give doses of the flea-killing compound.

When I moved to Atlanta, I brought my pennyroyal with me (as well as my echinacea and a few other prized plants). But I was sorely disappointed when I moved into a new house and my fresh pennyroyal plantings didn’t seem to keep away the fleas. I had to start using the chemical stuff again as the dogs were getting attacked. Apparently the plants have to be established and it takes time to drive the fleas away (it doesn’t actually kill the fleas, it just makes them want to leave.)

I made several cuttings last fall that over-wintered well and really took off this spring. Now I have several batches of pennyroyal growing in the yard, most notably in an area where my dogs like to hang out in the shade. There have been no signs of fleas. And I haven’t given my dogs chemical flea treatment in months and my house and yard remain flea-free.


28 Responses to “Repel Fleas With Pennyroyal”

  1. sharon sanborn says:

    when i first heard of pennyroyal, it was used for cattle, they walked under a covering that was saturated with it and the insects left them, so it was topical. then my friend had a kennel of smaller dogs and she used it topically, said only a drop, very powerful and may kill a small dog or pup. i live in fla, flea cap of the world, and i found pennyroyal in oil form at the flea mart. well i have been afraid to used it in any form for fear of killing my tiny ones, all our dogs are under 10 lbs. so, how do i use it, plant a bush, put it on the dogs. i have read up and it says it is not as powerful as peppermint. can you help me? please, this is the flea mart hear as noting is working, all my vet friends even are having a hard time, i have a yorkie that should be dead from all the chem i put on her. i finally applied eucalyptus. help sharon

  2. Slim says:

    Hi Sharon – I use the actual plant, not an extract or oil. I think all dogs are different but my dogs have never been interested in eating the plant. It is a member of the mint family and grows, looks and smells a lot like mint.

    I have found that transplanting or using a cutting is very easy to do if you dig a small hole and then cover the plant with a brick or large rock (to keep digging dogs from uprooting and killing it). I plant a sprig anywhere that my dog likes to hang out – by his dog house, under the shade tree, etc. It is very easy to grow. Once it is established in your yard fleas will just go away. It does not kill fleas, it just repels them. The bigger the area, the more you will need. It works best if your dog is confined to a smaller area (like a dog run or kennel).

    My back yard is approximately 22′ x 100′ and I have 4 different areas where the pennyroal is growing and that has been sufficient. I happened to find my plants over 10 years ago and have used the same ones for years. But you can buy seeds here:
    Good luck!

  3. Ulises Rubio says:

    I need to know where to purchase the pennyroyal in the Northern California area.

  4. Slim says:

    Hi Ulises,

    I found pennyroyal growing wild in the SF Bay area and that’s what I currently have now. You should be able to find it at any number of herb shops but you might want to try buying it online and grow it from seed. Given the historic (mis)use of pennyroyal extract being used for abortions, it might be more difficult to find the actual plant for sale in some areas.

  5. YASMINE says:

    Hello Slim
    I have purchased dried pennyroyal mint 1lb, ( very inexpensive ) and put small amount into the tea bag and left them on the floor.
    Just put seeds in my yard yesterday. I am hoping that they will grow successfully / sufficient just like your yard!
    me and my dogges are from Las Vegas and we never had flea problems there though, after moved to San Francisco, I think I was the worst victim of flea bites. Also, I dont use any harsh chemicals in the house, needless to say, difinitely not in my system and my doggies, a cat and cute bunnies.
    I have no choice to clean my house daily and hose up hot water in my yard to get rid of fleas, lavaes and eggs… In the mean time, I feel bad to kill them. Then I learned how to repell them!! It is just a wonderful idea not to kill, but repell them. Guilty free! I cant wait my pennyroyal grow so green in my yard.
    By the way, I found pennyroyal mint essensial oil at the health shop, though, I accidentaly touched it and I had a very bad reaction on my skin all over where I touched it. ( I put drops all over on my bed spread and then laid down there, watching movies… )

    Thank you for the great information.

  6. Slim says:

    Hi Yasmine – I hope you get your seeds to grow successfully. One easy way to grow (and protect) them is to put seeds or cuttings under a rock. Their roots will spread underneath multiply rapidly. It may take awhile for your plants to get established but once it is in your yard fleas will move out.

    Yeah the essential oil can be quite strong, especially if used full strength. You might try diluting it a bit.

    Good luck!

  7. YASMINE says:

    a rock??? I will try. Thank you!!

  8. Brenda Pron says:

    When using the penny royal esscence of oil as a topical for flea treatment and applying just 1 drop. How offen can this be done?

  9. Slim says:

    I think that depends on your dog and their ability to tolerate the smell – as well as any potential skin irritation. Personally, I don’t use the essence of oil because it can be toxic. I much prefer to plant the actual plants in the yard. It takes a lot of plants but you don’t have to worry about toxicity.

  10. Patrice Jantorno says:

    I have been trying to find out where to purchase the oil to make a flea collar for my pets. Anyone familiar with where to find it in the Magnolia, New Jersey area (close to Voorhees).

    Thank you.

  11. Slim says:

    Hi Patrice, thanks for stopping by!
    There are a number of places to buy seeds and essential oils online. I think CA has some shipping restrictions for the oil but I don’t think that exists for NJ.

  12. Gena says:

    Could you tell me what field you found it at I would really appreciate it. I live in San Francisco and need a small amount for a research project and as you know it takes some time to grow and finding it already grown and ready to purchase has proved to be very difficult. Thank you.

  13. Slim says:

    Hi Gena – thanks for stopping by! I lived in Glen park and it is almost impossible to tell you where this field is. My old neighborhood surrounded it and the only way you can get to it is via a backyard gate. But it is behind the houses on Capistrano Ave and Santa Rosa Ave.

  14. Michelle says:

    Someone told us to try this for the fleas but I am concerned about the effects it will have on our dogs. I see that you use it as a plant around your dog area, is that the best way to do it? My friend has some and told me that it is really toxic.Thank you

  15. jeanne says:

    I buy pennyroyal oil from Swanson’s vitamins on line. You can call them at 800-824-4491. I mix baking soda with the pennyroyal, citronella, rosemary and eucalyptus (one capful each) together in a 16 oz. jar and spread it on my carpets once a month. After 30 minutes or so I vacuum the carpet. Leave the vacuum running (after you’re done) for about five minutes seems to assure the fleas are dead. I live in central California and we have flea invasions several times a year. I have one cat only and the fleas eat me alive.

  16. joyce says:

    I wondered whether a small amount of pennyroyal essential oil when making soap would be good for pets’ fleabaths but, after hearing about how ingesting it can cause abortions I was concerned. The ratio for my soap batch is 1.5 oz. pennyroyal essential oil to 42 oz total of liquids (oil and water) and 5.5 oz. lye. Any comments?

  17. Hilda says:

    Interesting topic. I read years ago where a woman sewed cloth *tubes* & stuffed them with dried pennyroyal to use as flea collars for her cats! What a wonderful idea and its something I’ve been wanting to try! Your thoughts? Thanks!!!
    Hilda >^..^<

  18. Linda Woodruff says:

    I live in a rural area and have 4 indoor/outdoor cats. There is no way I can treat the areas they traverse and fleas and ticks are a major problem. I am really aftaid of the flea treatments on the market and am searching for a less toxic way to keep my kitties flea free. I read the use of brewers yeast and garlic powder is an option but my kitties won’t eat their food after I doctor it. Someone suggested a “tea” made from the pennyroyal leaves and sprayed onto the fur. That should be fun! Any other suggestions for cats?

  19. Slim says:

    Hi Linda – Thanks for stopping by! I too have heard the “spray” method with a pennyroyal tea but haven’t used it myself. My dogs spend their entire day outside and the back yard has several stands of pennyroyal. Fleas just don’t want to be there. For an inside pet, I would put cuttings in bedding and try to keep live plants nearby any favorite areas. Pennyroyal is great for repelling fleas and but once the fleas have settled in, it is much less effective.

  20. Slim says:

    Hi Hilda – yes! I think that’s a great idea but I have had better luck with the live plants.

  21. Slim says:

    Hi Joyce – yeah, the abortion thing comes from a time when herbal medicine was the norm. But from what I have read, it takes a very high does of some concentrated extract to do that much harm. A little oil in some soap is nothing by comparison and has been cheered by some as a great flea repellant. But the shelf life is relatively short. As much as possible, I recommend live plants. When it grows outside, the pennyroyal roots are very pervasive and really upsets a flea’s favorite place to live.

  22. Slim says:

    Great idea Jeanne – thanks so much for sharing!

  23. Buz says:

    I purchased a custom-made bar soap from a woman in Texas, which contains pennyroyal and citronella. I am now concerned that I may be endangering my 5 1/2 month old Aussie by bathing her with it. I had used a similar soap on my other Aussie many years ago, and never had a problem. Now I hear of the toxicity of pennyroyal and am concerned for her health. Is it just the basic oil of which I should be concerned, or is any amount of pennyroyal in a product, applied to the skin, harmful?

  24. Slim says:

    Hey There – thanks for stopping by! I haven’t ever heard of a topical application of pennyroyal causing issues. The toxicity of pennyroyal comes from internal ingestion (as far as I know) as it used to be a formula for terminating pregnancy. But the dose for that is very high and, again, would have to be ingested. Pennyroyal tea (not the song) has been used for centuries much like related mint as it helps ease and upset stomach, among other things. You can read more about that here. I wouldn’t worry about topical application though.

  25. Patty says:

    I saw that pennyroyal was especially more toxic to cats than dogs. be careful

  26. Slim says:

    Thanks for your comment Patty. I would point out that essential oils are much different than the plants themselves. The essential oils are highly concentrated extracts and are definitely toxic. Ingesting a couple of tablespoons of essential oils is very toxic, but so is ingesting a couple of tablespoons of table salt.

    I don’t recommend anything other than planting the live plant around areas where dogs stay (outside). I’m not sure about cats but have read they are attracted to pennyroyal because of the similarity to catnip, another plant in the mint family. But if there is evidence of animals being poisoned by just the plant I would be very curious to read that if you can share.

  27. Shelda says:

    I purchased the oil and diluted it, equal ratios of the pennyroyal oil to water. Got a q-tip and dabbed the outside of my pets collars (3 cats, and a dog). I also purchased brewers yeast w/garlic tabs, and have DE ( Diatomaceous earth) I am in great hopes, that this natural approach, helps me get these fleas under control, and eventually eliminated! If anyone can give me any more advice, I’d greatly appreciate it!

  28. Chrisitne says:

    My mother used to use pannyroyal as a dip for her pets when I was a little girl. Her dogs never got sick and never had health problems what so ever. Also if you put the pennyroyal oil on their collar it will prevent it from getting to the skin if you are worried about that.

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