Ask the Veterinarian/bio spot


QUESTION: What do you think of the flea killer permethrin?

ANSWER: hi there,
Permethrin is fine in dogs, but not at all safe in homes with cats. Permethrin is based on the natural pyrethroids from plants that repel insects, ticks and fleas. Can be very effective in dogs with flea allergies, in fact it was recommended for daily use as a spray all over for flea allergic dogs by our dermatologists until Comfortis came out.

The limitation is that it is often a bit stinky and needs to be constantly reapplied as often as daily, but for mild problems weekly can be fine.

Does that help? Let me know if you need any more specifics.


Dr. Eloise Cotton

---------- FOLLOW-UP ----------

QUESTION: The permethrin flea killer i found in the store is called put it on them monthly as a spoton treatment?

Sorry for the delay, I went away for a few days and didn't check the computer.

We don't have this particular product and I have my doubts as to whether monthly treatment would be sufficient. I suspect it might not quite keep up if you have a high-flea area or a very flea-sensitive dog.

My favourite flea products are Comfortis and Advantage monthly as they work very quickly and will last a full month. If you did use biopspot, if you combined it with some good environmental flea control, it might work. There is some information here about fleas in an article I wrote.

Hope that helps.  

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Eloise Bright


I am a vet with a special interest in dermatology, particularly allergic dogs and cats, behaviour and acupuncture. I work mainly with dogs and cats. If you are wondering why your pet is still itchy, despite good flea control, or why your dog licks his feet, I may be able to give you some solutions. I'm currently very passionate about behaviour and am doing some further education in this area. So if you have a troubling behaviour with your dog or cat, such as barking, leash reactivity, anxiety or a dog who is a little wild and difficult to control, I may be able to help you with some solutions.


I work in an area of Sydney where we see lots of allergic pets. I think behaviour problems are very common and I help a number of owners find solutions that will restore peace to them and their pets. Currently I enjoy answering questions, providing advice and writing pet care articles for

I graduated as a vet from Sydney Uni in 2006 and have since been completing my Masters in Small Animal Practice and am also updating my skills with a behaviour course through Sydney Uni.

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