Flea treatments and rivers: UK government rejects 28-day swimming ban for treated dogs — what the research shows

What the government decided

On 26 October the Department for Environment, Food and Rural Affairs (Defra) responded to a House of Lords report on how pet parasite treatments are polluting rivers. The government accepted most of the recommendations. But it rejected the main one — to stop treated dogs from swimming in rivers and lakes for four weeks rather than the current four days.

The chair of the Lords committee, Baroness Sheehan, called the decision disappointing. The committee intends to raise the issue in a debate with the minister.

How flea treatments get into rivers

Many spot-ons and flea and tick collars contain fipronil or imidacloprid. These are insecticides that act on insects' nervous systems. They have long been banned or heavily restricted in agriculture in the EU and the UK because they harm bees and aquatic invertebrates — but they remain in veterinary products for dogs and cats.

From an animal's coat, these substances reach water in two ways: directly, when a dog swims in a river or pond, and via the drains — when a dog is bathed, its bedding is washed, or its owner washes their hands after stroking it. Sewage treatment works remove these substances only partly.

Why these treatments are needed at all

Giving up parasite protection is a bad idea. Ticks transmit diseases that are dangerous to dogs — babesiosis and Lyme disease (borreliosis) — and as the climate warms, their season in Europe is getting longer. Fleas cause severe allergic dermatitis and carry tapeworm and bacteria that can infect people too. So the UK debate is not about stopping treating animals, but about doing it sensibly.

Types of treatment

• Spot-ons — the most common type. The substance spreads over the skin and coat, so some of it washes off when the dog swims or is bathed.
• Collars release the active ingredient gradually over several months.
• Tablets work from the inside and don't wash off the coat, but they have their own limitations and contraindications.
• Shampoos and sprays work for a short time and are mostly used for one-off treatments.

Which type suits a particular dog or cat depends on its age, health, lifestyle and which parasites it needs protecting from. It's a decision best made with your vet.

Important: products for dogs must never be used on cats. Some spot-ons for dogs contain permethrin, which is toxic to cats and can cause seizures and death. If you have both a dog and a cat, ask your vet which product is safe for both, and don't let your cat lie right up against a freshly treated dog.

What scientists found

In 2024 researchers at the University of Sussex and Imperial College London traced how treatments get from dogs into the sewers. They took samples from 98 dogs that had been treated with fipronil or imidacloprid spot-ons, and from their owners.

Both substances were found in every rinse sample. The most surprising finding was the contribution of owners' hands: traces of the products were detected on hands at least 28 days after the dog was treated — simply from stroking the pet and then washing their hands. The largest single loss comes from bathing the dog: the authors estimate that around 5% of the applied imidacloprid and around 3% of the fipronil go down the drain this way. In total, handwashing, bathing and washing bedding account for an estimated 20 to 40% of these substances in wastewater.

What the Lords proposed

In August the House of Lords Environment and Climate Change Committee published its report "Paws for Concern" on pets, parasite treatments and pollution, with eight recommendations. Committee members heard evidence that spot-ons may pollute water for up to 28 days after application, so they proposed:

• extending the swimming ban for treated dogs from four days to four weeks;
• selling parasite treatments only after an individual consultation;
• better training for vets and retailers;
• funding new research;
• assessing the environmental risks of products more strictly;
• publishing anonymised data on sales and use.

Why the government rejected 28 days

Defra believes there isn't yet enough evidence for such a ban. The studies involved small numbers of animals and rely on assumptions about how dogs behave, what waterways are like and the conditions under which products are used — real life may be different. In the department's view, any new restrictions must be based on an established scientific method of risk assessment.

There are other arguments too. An overly long ban could harm animal welfare: some owners might stop treating their dogs altogether or choose less suitable products. New rules could also lead to different products being sold in Great Britain and Northern Ireland.

The current advice, combined with guidance for owners, remains the most proportionate approach while we review new evidence.

Defra, response to the House of Lords report, 26 October 2026

What the government accepted

The department backed the other proposals: training for professionals, research funding, tougher environmental assessment of products and publication of anonymised data on sales and use. Whether parasite treatments should be sold only after a consultation with a vet is currently being considered by the Veterinary Medicines Directorate, and Defra did not want to pre-empt its decision. The results of a spring consultation on the issue are due to be published in the coming weeks.

Does this affect other countries?

The same active ingredients are in products sold throughout Europe, and rivers work the same way everywhere. The UK debate is one of the first in which regulators are seriously discussing how to protect water without leaving animals unprotected against fleas and ticks. Dog and cat owners in any country would do well to follow how it turns out.

How to tell if your pet has fleas

Fleas are hard to spot: they're small and quickly hide in the coat. Warning signs are frequent scratching, nibbling at the skin at the base of the tail, redness and bald patches. There's a simple test: comb your pet's coat over a damp sheet of white paper. If black specks are left behind that spread into reddish-brown smudges, that's flea dirt — digested blood. In cats fleas are even harder to find: they groom thoroughly and swallow the insects, so sometimes the only sign is rice-grain-like tapeworm segments near the tail or in the litter tray.

Fleas on the animal are only part of the problem. Eggs and larvae drop off the coat and develop in bedding, carpets and cracks in the floor. So as well as treating your pet, regularly vacuum where it sleeps and empty the vacuum bag or bin outside.

How to check your dog for ticks

Ticks are most active in spring and autumn, and in mild winters they can be found in December too. After walks through grass, undergrowth and woodland, check your dog: ticks most often attach to the head, ears, neck, armpits, groin and between the toes. Remove a tick with a tick hook or tweezers — slowly and steadily, without squeezing it. Don't smother it in oil or burn it: that doesn't help and can do harm. If the bite site becomes red and a few days later your dog becomes lethargic, develops a temperature or dark urine, see your vet urgently — this can be how babesiosis starts.

How to treat your pet without harming rivers

There's no need to give up parasite protection: fleas and ticks carry dangerous diseases, some of which can also pass to people. But there are things owners can do themselves:

• Agree a plan with your vet. Many veterinary organisations advise treating according to actual risk — taking into account the season, lifestyle and region — rather than all year round "just in case".
• Follow the instructions. If the leaflet says not to bathe your dog or let it into water for a few days after treatment, stick to that.
• Don't bath your dog straight after applying a spot-on unless you have to: bathing washes off the most product.
• Try not to touch the application site and wash your hands after treating your pet.
• Don't double up. A spot-on, a collar and a tablet at the same time don't give double protection, but they do increase the load on the animal and on water. The dose is based on your pet's weight.
• Don't pour leftover product down the sink or toilet — dispose of packaging as the leaflet or your local council advises.

The government's decision is not final: work on new evidence is continuing, and advice for owners may change.