Pesticides: how to make the right choice

Pesticides on the market are many, so it is not so easy to choose the right one, you will find them in pharmacies, specialized shops and veterinary clinics. I would like to help you not to make mistakes.

Parasites that can infest dogs and cats are many and with different consequences, from simple itch to transmission of serious and severe illnesses.
The best care I recommend you is prevention, therefore from end of March till end of October, pesticides are crucial for your four-legged friend's protection.

What product to use?

It is important to take into consideration the parasite type but also the component of the pesticide. On the market you will find spot-on, collars, spray, shampoo and powders. Let's see them in detail.

  • Spot-on: they are active on fleas, ticks and lice, some even on mosquitoes, sandfly and horsefly for a period of time that covers 3-4 weeks, depending on brand. They can be easily applied on the area between the shoulder blades, where the dog won't be able to lick it away, and it's important that the application is done on the skin and not on the fur.

  • Collars: they slowly release an active toxic substance on fleas, ticks and some collars even on mosquitoes and phlebotomists, for some months, depending on the brand. Other ones, instead, release on the skin a toxin able of killing the flea that will try to bite the animal. Their limitation is given by the fact that they protect well the area close to the collar (head and neck) and are less effective on the more distant areas (legs and torso). It is important to choose the product based on the size of your animal and remove it immediately, in case you notice an irritation of the skin in the area of application.

  • Shampoo: it is perfect for the removal of adult parasites; the type of product (low contact time and rinsing), lowers the risk of toxicity but obviously makes it less effective to protect from infestations for a long time, it lasts a few weeks depending on the animal's habits (where he lives, how much he gets wet ...). The way you use it is very important; you have to apply the product starting from the neck, in order to create an obstacle to fleas, not to let them nest in the areas behind the ears. Then proceed along the body, insisting in particular on the areas where the animal scratches himself and then proceed to a thorough rinsing. The most of shampoos on the market are cosmetic products because they contain only essential oils and detergent ingredients listed in the so-called INCI (list of ingredients) and therefore they don't carry out targeted action on parasites. The ones which are effective to eradicate parasites contain active biocides substances (able to eliminate microorganisms) that appear listed with a ministerial authorization (AIC n° ...)

  • Spray and powders: these products are very useful to disinfest environments from fleas and lice (pet beds, carpets..) and their action lasts from few weeks to a few months according to the used brand. Instead, their use on pets is uncomfortable, because it's difficult to well spread the product and besides there is a high risk to inhale it and ingest it.

How does a pesticide work?

There are 3 different families of active substances, everyone suitable to different parasites or different species:

  • Fipronil: it's an active substance contained in products such as Flevox or first Frontline; it acts by quickly repelling adult parasites of ticks, fleas and lice (24h for fleas and 48h for ticks), it doesn't kill eggs and larvae. The duration of the protection is of 30 days for ticks and 90 days for fleas and lice.

  • Fipronil + S-methoprene: it's the active substance of Frontline Combo that, like above, has the same level of protection. The difference with the previous one is the presence of S- Methoprene that acts on eggs too, inhibiting the consequent growth of larvae. The action will be indirect also on environment, preventing the reinfestation for at least 8 weeks.

  • Permethrin: it's the active substance of Exspot spot-on, indicated for treatment of the main external parasites (fleas, lice, ticks and mosquitos). It must be applied exclusively on dogs and on puppies being at least two weeks years old. Warning: it's toxic for cats.

  • Fipronil + Permetrina: this one is highly toxic for cats, it is contained in the pesticides for dogs like Frontline Tri-Act and Virbac Effitix.

  • Imidacloprid: it's the unic active substance of Advantage, repellent pesticide in spot-on for cats and rabbits. Useful in case of allergic dermatitis from fleas.

  • Imidacloprid + Permetrina: it's contained in Advantix products, to use only for dogs protection. It acts quickly (in 24h) killing adult parasites and it has a repellent effect until exhaustion of substance. It is water resistant and it is valid for 30 days.

  • Imidacloprid + Flumethrin: it is the combination of active substances of the dog's Seresto collars; it works also on sandflies, flies, mosquitoes, fleas, ticks and lice. it's ideal for the protection of your four-legged friend even against Leishmaniasis, it offers protection up to 6 months if correctly used.

  • Deltamethrin: it's the active substance of pesticide collar Scalibor for dogs. Deltamethrin acts quickly when it comes in contact with the parasite. It can be used combined with fipronil and has multiple effects:

Repellent effect: mosquitos tend not to get close to host.
Knock-down effect: insects that manage to get close to the host are affected by motor incoordination.
Anti-feeding effect: the neurological signs prevent feeding.
Lethal effect: parasite is killed.


Natural remedies: do they work?

Nowdays on the market there is a great variety of natural pesticides. There are many essencial oils with repellent properties (thyme, eucalyptus, lemongrass, geranium...)  but keep in mind that not always everything that is natural is risk and danger free and to up to now there is no documented studies for effectiveness on parasites and on health safety of our pets. One of the best current products is Neem oil which is considered, in veterinary field, a valid pesticide with repellent action against mosquitoes, sandflies, fleas, ticks and lice. It can be used as a spray, pure or added to shampoo.
The limit that you must consider is that, if the chemical pesticide has an immediate and lasting "effect", natural products are not so fast. Their action, to be complete, must work in synergy with other pesticides.

Most of these products will be part of, as already mentioned above, cosmetic products (they will have a list of ingredients, INCI), they will report repellent sign, repellent shield, remove insects, but they will not contain any effective active ingredient authorized by the ministry. It is important to always read labels, according to these concepts, to choose the product that best suits your needs.

How to use pesticides?

Given their characteristics, we can not expect these products to be harmless! Here are some tips to use them properly:

  • Always use the dosage based on the precise weight of your pet
  • Follow the use advice shown on the label
  • Be careful not to use products for dogs on other species. Some can even be fatal if used for example on the cat!
  • Never use them on a sick or debilitated subject, ask your vet for advice first
  • Do not use different products at the same time which would otherwise increase their toxicity (eg shampoo and collar)
  • Ventilate the environment after using these substances
  • Keep them out of reach of children and pay attention to contact with the product if it is just administered to the animal
  • Always follow the administration instructions well, avoid contact, use gloves, do not inhale ...
  • When you spray the product into the environment, cover any terrariums, aquariums to avoid contamination.


Now you have all the basics to buy a good pesticide. I hope this has been useful. See you next time!


Eleonora Bosoni

Dr. in Veterinary Medicine




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