In recent years we have been focussing on the impact that farming has on the environment with the use of chemicals, antibiotics, and anthelmintics (worming treatments) under scrutiny. So it is only natural that our thoughts should turn to animals closer to home too. The advice has always been to use regular preventative parasite treatment on our pets to protect the health of that individual. But what impact might this be having on the environment?

Are flea treatments a problem?

Recently there have been questions raised as to the impact that flea treatment has on environmental contamination and insect populations. After all, flea treatment is insecticidal which is how it does its job of killing fleas (a wingless insect parasite). There is a risk these products could affect other insect and invertebrate populations too, causing harm to eco-systems. Recent studies have shown increased levels of two chemicals, fipronil and imidacloprid, in rivers which is a worry. Concentrations of these chemicals are particularly high just downstream of waterworks. Suggesting that these chemicals are coming down sewers through treated pets being bathed at home, and possibly through inappropriate disposal of these products too. 

Fipronil is a product readily available to the general public as an over-the-counter flea medication, with no veterinary prescription required. This means it is probably one of the most common flea products used. 

What could be done about it?

One idea proposed is to tighten regulations and make this drug prescription only to help manage its use more appropriately. Another idea is to consider using targeted parasite products rather than using these chemicals prophylactically all year round. This does have the downside that your pet would not be protected against parasites all year round, and would have to catch them before treatment can be implemented. This idea is sound in theory, but having seen the real difficulty that some owners face when trying to get rid of a full blown flea infestation, it’s hard to see that we could legitimately go back to this. Most owners are now very diligent at ensuring their pet’s preventative parasite treatment is up to speed and the health of our pets is foremost in our minds.

So instead of not treating pets at all; perhaps we should look at some of the individual products we are using instead?

Spot-on products

Spot-on flea treatments are probably the most common product used on our pet dogs. There are a variety of spot-ons used including, but not limited to, those that contain fipronil and imidacloprid. The advantage of spot-on treatments is that they are very easy to administer, with an application of a small volume of liquid to the back of the neck once a month (for most products). Many of these products protect against multiple parasites. The disadvantage of spot-ons is that they can get easily washed off. Especially if your dog is bathed or goes swimming in the first 48 hours of having the product applied. Regular swimming or washing is known to affect how well the product works – and how much environmental contamination there is.


Flea and tick collars can often be purchased without a veterinary prescription. Some of these collars can last several months which provides ongoing protection even in the face of forgetful owners! Some collars are water-resistant and so can be worn whilst swimming or being bathed. However, one popular product contradicts this by stating ‘This product should not enter water courses as it may be dangerous for fish and other aquatic organisms’. This raises some environmental questions, especially if you have a dog that spends most of its time swimming.


There are different types of flea tablets available for dogs, some of which cover other parasites like ticks too. These tablets are ingested by your pet and protect for up to 3 months in the case of some tablets. The advantage of tablets is that your dog can swim and be bathed without it reducing the efficacy of the product. This is because the molecules are held within your dog’s skin, rather than being applied on the surface. Of course, some dogs will refuse to take tablets, which can make life tricky. In the datasheet for one of these tablets the active ingredient, Fluralaner, is stated to be excreted almost unchanged in the faeces so there may be more studies required into the environmental impact of this too.

So which is best?

By comparing the three most effective methods of flea prevention, it would seem that flea tablets are likely to be best for the environment as any medication will not leach out into watercourses. However, as with all areas of current interest, there is still more research to be done. It is best to speak with your veterinary surgeon to balance the individual needs of your dog alongside any environmental concerns. Bear in mind that prescription products are more likely to be effective than supermarket equivalents. So a trip to the vets is always well worthwhile. Your vet will have the pet’s interests at heart when recommending various prophylactic products. But it is worth raising any concerns you have with them as a discussion point.

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