How can you treat your pet for fleas without harming nature?

The Guardian

18-02-2025

The chemicals used in standard flea treatments are polluting waterways and having a drastic effect on wildlife in the UK, killing songbird chicks.
Vets usually advise owners to treat their pets every month or so, even if they do not have fleas, but scientists are now urgently calling for the government to reassess the environmental risk of pesticides used in the treatments and to restrict them.
The Guardian has spoken to experts to find out what pet owners can do to prevent a flea infestation while minimising the impact on the environment of regular treatment.
Topical flea treatments, often referred to as spot-on products, are capsules of liquid that contain insecticides. They are typically applied at the back of a pet's neck so they do not lick them off, according to Elizabeth Mullineaux, president of the British Veterinary Association.
The insecticides are distributed through the grease glands of the coat and into the pet's hair, making it toxic to fleas for one to three months.
While there are a range of flea treatments, the two most common are imidacloprid (a neonicotinoid) and fipronil. Both chemicals are banned from outdoor agriculture to prevent the pollution of waterways.
While some are available over the counter, flea treatments are often sold as part of pet healthcare plans by vets.
Research at the University of Sussex has found that pesticides used in regular flea treatments are in 98% of English rivers, often at levels far higher than those deemed safe.
Some of this is from treated dogs swimming, but much goes down the drain from households, (eg from shampooing dogs, washing bedding, stroking and washing hands) and then enters rivers, according to Dave Goulson, professor of biology at Sussex, who co-authored the study and supervised the research.
Recent research also found that 100% of blue tit and great tit nests are contaminated with pesticides from pet flea treatment, as the birds collect fur from dogs and cats to insulate their nests. The study, funded by the charity Songbird Survival, found that nestling mortality is associated with higher levels of the pesticides.
'Other products used in flea treatments have not raised the same environmental concerns as fipronil and imidacloprid but we don't necessarily have all the environmental data to say they're absolutely environmentally safe,' said Mullineaux.
The most important thing owners should consider is whether their pets need topical treatment and, if so, how often and when, and if there are alternatives, say experts.
Mullineaux said: 'Speak to your vet about the best way to use the products for your pet, and your circumstances and risk level. For example, the sorts of questions we might ask you are how much a pet goes outside, if you have other pets, if anyone in the household is particularly medically vulnerable, and what your pet's lifestyle is like – whether it swims or goes for doggy daycare, or whether you need to wash and groom it a lot.
'We strongly encourage vets and owners to take a risk-based approach to prescribing or recommending these medicines, reflecting an animal's exposure to parasites.'
If spot-on products are considered the only appropriate form of treatment, you should brush your pet indoors or in a sheltered area where you can gather the hair afterwards and dispose of it in a sealed bag.
'What we don't want is the hair blowing away and birds collecting it up as nesting material. I think a lot of us have probably thought that was kind of quite a nice thing for birds to do but clearly it really isn't if the hair is contaminated with chemicals,' said Millineaux.
It is also important to take care of packaging material, particularly from spot-on products. 'I've heard horror stories of people washing out the little containers, which obviously do contaminate water,' added Millineaux.
'What we want to be doing is not washing them out but disposing them of them in something like a seal bag and following any manufacturers guidelines.'
Washing is discouraged for several days after treatments, owing to the risk of product getting into waterways.
There are plenty of suggestions for alternative methods of treatment – lavender oil, vinegar, rosemary oil, etc – but scientific evidence for their efficacy is scant, and some essential oils can be toxic for dogs.
'When I've seen people trying to use these things, they can actually end up with massive flea infestations, which result in us using even more chemicals on both the pet, but also having to use it around the house as well,' said Millineaux.
While there are still concerns over the environmental impact of oral medication for flea prevention, Ed Bailey, chair of Vet Sustain, an organisation that supports vets to change towards a more sustainable future, said there may still be a better alternative to spot-on treatments.
'You might choose to use an oral product rather than a topical product to avoid the risk that we're seeing with some of this emerging research … the two big bits of research that have come out recently are about ficronil and imidacloprid in wastewater, and were associated with owners stroking their pets and then washing their hands or washing bedding or directly washing the animal within the home and then [the product] going into wastewater.'
Injectable products can also be used as a more environmentally friendly alternative to spot-on treatments. Liz Broadbelt, a retired vet from Ceredigion, advises cat owners to use injections that offer six-month-long prevention and control of flea infestation.
'I have two cats. They are indoor and outdoor and, for many years, I have used injections every six months to control fleas. This is not an insecticide and works by blocking the development of flea eggs into adults. It doesn't kill adult fleas. The main problem with flea infestation is the production of hundreds of flea eggs in the environment. I think this is a much more environmentally friendly way to control fleas, since it does not affect other invertebrates.'
If you don't want to treat your pet at all, then washing it weekly, washing the bedding, and vacuuming your house can be beneficial to remove flea eggs, Bailey says.
'The advice would be around treating your pets in a more similar way to treating your children, in that you would check your kids for nits. You would use a nit comb but you don't treat the kids every month for nits regardless of whether they have it. A flea comb can be beneficial for assessing whether or not there is an infestation present.'