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Dear Dr. Narda ~

I just purchased a product from the health food store that claims to be an all-natural flea shampoo for cats and dogs. The main ingredient is pennyroyal oil.  They claim it kills fleas and even some ticks.  Is it safe to use? ~ Cat Lover in IndianapolisPennyroyal

Dear Cat Lover ~

In short, no!  Please do not use this product.  Pennyroyal is indeed natural, but not all that is natural is safe.  In fact, pennyroyal can be quite dangerous, even deadly.  Read more here in an article I wrote back in 2009 in Veterinary Practice News: “Top 10 Holistic Traps”.  See #5.  Also see this article from This is why it’s IMPERATIVE that veterinarians and physicians, as well as the general public, has access to factual, scientific analyses of botanical remedies.  Some plant compounds are safe, but many are not.  And, what is safe for one person or animal may not be harmless in another.  We need to take into consideration how the plant was grown (i.e., is it a root cultivated next to a paint factory in China that has released cadmium and other heavy metals into nearby soils), whether it causes herb-drug interactions that might make medications also being consumed either more toxic or inactive, and whether there might be a better non-herb, non-drug solution through integrative physical medicine approaches (e.g., acupuncture, manual therapy, exercise, photomedicine, etc.).

I’m so glad you wrote to us before using this product!

~Dr. Narda Robinson