The Issue with Permethrin…

Thanks go to Daisy’s Human, Louise, for sending us this story in the hope that it will publicise the need to check exactly what you are giving your guinea pigs and to underline the fact that it should not be Permethrin! All medicines have side effects and all guineas will react differently and with varying degrees of sensitivity but where there is a safer option use it! Because guinea pigs are such small animals needing small doses usually medicines are often decanted into smaller vessels which may mean you are not automatically given the contraindications etc, ask for them, you are within your rights, even if you forget at the time, ring the surgery and ask or search for the product online, it will be there. NOAH Compendium ofAnimal Medicines is a good place to look.



“After discovering a mild infestation of mites in my four piggies, I treated them with a spot-on treatment called Xenex Ultra. Unfortunately I had confused this with the treatment I had used in the past, another spot on called Xeno 450. It was only later that I realised the Xenex Ultra contained the active ingredient Permethrin instead of Ivermectin.


The morning after treating the girls, they were all in a terrible state of anxiety, in particular Daisy. She was hurtling around the cage, screaming as if in pain. She kept banging into the walls and the other pigs. All of them were chattering their teeth and a huge fight broke out with her sister, Mabel.


I took Daisy to the vet immediately. I wasn’t even able to pick her up and ended up having to get her in the vet carrier by throwing a towel over her. The vet was very familiar with this terrible adverse reaction to Permethrin and had seen it quite often in the past. It had caused Daisy to become anxious, aggressive, hyper-active and hyper-sensitive to light, sound, noise and touch. The vet informed the drug manufacturer but other than washing off any remaining spot-on, there was little else they could advise other than take her home and try and keep her quiet.


Over the next few days, we treated Daisy with rescue remedy to help calm her down, but she basically lived under a towel in a separate area of the cage until the drug had worn off. It took about 5 days until she was happy to come out from under the towel and walk around normally.


It has been several weeks now and its starting to look like Daisy and Mabel may never be able to live together again. Before using this drug, all four girls lived very happily together for over 2 years. Both Daisy or Mabel don’t seem to be able to forget the huge fight they had the morning after using the Xenex Ultra. At the moment every reintroduction ends up in another fight with teeth chattering and them lunging at each other with all their teeth bared. Anyone that has a lovely group of chilled-out and bonded piggies will know how heart-breaking it would be for this to happen. I’ve never seen a hint of aggression in any of my piggies until using this drug, it really seem to have changed their personalities. I’ve been bitten myself more often in the last 3 weeks, then in the whole 10 years I’ve had piggies as pets.

I really want to stop other pigs (and their owners) having to go through the same thing and the best way to do this is to make sure any reaction to a product is reported. The first people to tell is the Veterinary Medicines Directorate or VMD. These are the people who make sure animal medicines are safe and effective. They have an online or paper form which you can fill out and can be found here:

I think it is also important to make sure the drug manufacturer also knows about the reaction. You can find the manufacturers contact details by searching on the NOAH website (National Office for Animal Health)


After checking through my cupboards I found another two products containing the same active ingredient, Permethrin (Johnsons Insecticidal Shampoo and Johnsons Insecticidal Spray). It is used in lots of other products other than Xenex Ultra, so please check the labels carefully.


This whole incident makes me so sad and I wish I could turn back time and have never used the Xenex on my piggies. I hope telling Daisy’s story will help to warn other people about the dangers of using Permethrin on their guinea pigs.”



The correct treatment for mites is to give an Ivermectin product, Xeno 450 for guineas over 800 gms and Xeno 50 for guineas under 800g are the correct ones, on day one and day ten and a bath in a Gorgeous Guineas’ shampoo as instructed.


Thanks to Gorgeous Guineas for these definitions:

  • Pyrethrum is a natural insecticide that comes from the flowers of specific species of Chrysanthemum.
  • Permethrin is a synthetic version of Pyrethrum with the chemical constituents based on those found in natural Pyrethrum. It is this synthetic version that is most often used in insecticidal products because it is far more stable in sunlight. Natural Pyrethrum breaks down in about 12 hours, but Permethrin is far more stable and longer-lasting at 30 days plus.

Read the Gorgeous Guineas’ blog post on this story here:

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Daisy and friend


Lazy Daisy




February 19, 2013   Posted in: Fungal and Parasitic Skin Problems, Health, Inside The Hutch, Miscellaneous, Planet Guinea, The Pig Issue