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Spot-On Treatments and the Environment: What Every Pet Owner Should Know

by | Jun 18, 2025

Pet Flea Treatments and Our Environment: A Growing ConcernCat on a lead walking by a river

Recent studies have highlighted concerns about the presence of chemicals from pet parasite treatments in UK waterways. These treatments, commonly used to prevent or kill fleas and ticks on pets, contain toxic chemicals that are making their way into UK rivers and ponds, particularly in urban areas.

Pet owners are understandably concerned about this issue. Firstly, as animal lovers, it doesn’t seem right to be contributing to environmental pollution, and secondly, there is a question of whether these products are safe for the pets themselves and their human families. Let’s examine what is known about this topic to date.

⚠️ Imidacloprid and Fipronil: What Are They and Why Does It Matter?

Imidacloprid and fipronil are two of the chemicals found in UK waters. Both are toxic to aquatic life and insects but not mammals, if used according to instructions. The contamination of the environment is primarily attributed to the use of spot-on treatments for pets that contain these ingredients. These treatments are applied directly to the skin of pets, and the chemicals can wash off during bathing or when pets swim, eventually entering the water system.

Why Flea Control Is Still Essential for Pet Health

Does this mean that by treating and preventing flea infestations in our pets we are acting irresponsibly? Absolutely not. Fleas are very harmful to dogs and cats. Not only are they a nuisance, but they also cause a very common and distressing allergic skin disease called Flea Allergic Dermatitis, as well as spread a tapeworm called Dipylidium caninum, which can infest both dogs and cats. Young kittens can die from flea-induced anaemia.

Finding the Balance: Protecting Pets Without Harming Nature

All this information means we need a balanced approach to pet parasite management that considers both animal health and environmental protection.

In the author’s professional opinion, we can do both safely – prevent flea infestations in pets and protect our environment.

What About Cats? Are Spot-On Treatments Still Safe?

Firstly, most cats do not swim or get bathed regularly, so spot-on treatments are still commonly used. However, it’s important to be mindful that the chemicals can still enter waterways indirectly—such as through handwashing after application, laundering bedding, or waste entering the sewage system. Care should always be taken when using these products, wearing disposable gloves when administering the treatment for example, and disposing of them in household waste, as well as avoiding touching that area for 2-3 days. For those who prefer an alternative, there is a tablet form of parasite control for cats, though it carries the same environmental precautions as oral treatments for dogs.

dog by river

What Are the Alternatives for Dogs?

But what do we do with dogs? Luckily, we have other choices. A range of very effective oral treatments for dogs exist that are excreted with faeces. All that owners need to do to prevent environmental contamination is to continue to pick up their dog poo. Be particularly vigilant in the 48 hours following the oral treatment. This reduces the risk of active agents entering the environment.

Talk to Your Vet: Tailored Advice for Responsible Protection

These treatments are prescription only – ask your vet what is the best option for your pet’s individual needs

Written by:

Dr Kate Russell Cert AVP (ECC) MRCVS

Veterinary Surgeon, Certified RECOVER CPR instructor

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