A bit more insight on pennyroyal: An aside - interesting in the last FML that Sukie and I appear to disagree on the safety of pennyroyal. As I indicate that it can be used safely, her Herbal PDR research suggests hepatotoxicity and the possibility of abortion. Well actually, both answers are correct, but more explanation is in order. Pennyroyal is a substance that has been used for thousands of years as an herbal flea repellent. Derived from the leaves of the pennyroyal plant, the active ingredient is pulegone - a word derived from the Latin word "pulex" meaning flea. The key to the toxicity of pennyroyal (I'm not talking about efficacy, only toxicity), is like most things - how much you give. The one dog wth reported pennyroyal toxicosis in the literature received a dose of 60ml of a preparation of 100% pennyroyal topically, (the owner had picked it up at a health food store. This is equivalent to approximately 2000 mg/kg of pennyroyal topically. Pennyroyal oil when ingested by humans is toxic at a dose of 500 mg total (but that's another species entirely, and it was ingested.) Also, it is likely that an animal doused with the stuff may ingest part of it. Pennyroyal oil is used as an abortofacient in humans, and is generally taken orally. There are no animal studies on the toxicity of pennyroyal available. Now why would I say that the material is generally safe? Actually, it is a common compound in many herbal flea remedies and has been for years. In such remedies, it is present only in very small amounts, not enough to cause toxicity (and is usually mixed with small amounts of other herbal remedies.) However, when used straight, or if the commercially available flea compound is used in high enough doses, toxicity may result. Plus, most formulations are available for dogs, so caveat emptor when crossing species lines. Lest anyone think that pennyroyal is the only flea product that may be toxic, the answer is that ALL of them, given in high enough doses, may be toxic. We employ toxic products to kill fleas - the trick is not to give it in sufficient amounts to cause toxicity in the animal, too. Organophosphates and carbamates, though rarely used today are common examples of toxicants used in flea shampoo. I remember as a young man, working as a groomer in a vet's office, that I would douse the animals with malathion (!!!) not knowing that this drug could lead to marked toxicity to both the animal and the young groomer! Today's products, like lufeneron and pyrethrin have much higher levels of safety, which is increased by the fact that a single doses are prepackaged, and it takes a real dummy to cause toxicity. I have a question for anyone considering the use of pennyroyal for flea control in ferrets or other pets - WHY? There are far more effective products available through your vet. Toxicity is a serious issue, but efficacy is also important. Chances are, at safe dosages, these products are of little use in flea control. Fleas really don't care much about odors. With kindest regards, Bruce Williams, dVM [Posted in FML issue 3261]