Pet Factsheets

Flea control

Fleas are the most common parasite found on household pets and every cat and dog is likely to be infected at some stage in its life. However, with the advent of modern products it is possible to prevent fleas from becoming a problem in your home. Working closely with your vet, who will give you advice on how to use these products effectively, you will be able to stop these nasty little insects making a meal of your pet and you!

Why do I need to treat my pets for fleas?

Fleas can be a real menace in centrally heated homes, particularly if you have more than one pet. They are the most common cause of skin disease in cats and dogs: as well as the general itchiness and irritation from bite, some pets are allergic to flea saliva and can react quite severely to even one bite. Unfortunately, fleas are not too particular and will happily bite you and your family if they can't find a convenient pet!

How can fleas be controlled?

To ensure your home is free from fleas you must control them on your pets and in the environment.  Fleas are tricky for two reasons: they can jump from pet to pet and from pet to human, and they also spend only 5% of their lifecycle on the pet, with the rest of the time spent living in your home, waiting for a good moment to re-infect your pet.

There are many products available to kill adult fleas on pets. These products have different active ingredients and work in different ways - some are more effective, work faster or longer than others. There are many ways of applying the products and you should be able to choose something that you find convenient and simple to use. Prices of products may vary but the most convenient and effective are usually more expensive. If your pet is allergic to fleas, it is very important to prevent any flea bites, so you should use a product which kills fleas rapidly.

Products for controlling fleas act in 1 of 3 ways:

1. Chemicals which are toxic to the adult flea: These products are usually applied to the animal's coat and poison any flea that passes through, but oral products and collars are also available. Some chemicals can also be applied to the house so that fleas can be killed whilst they are away from the pet. Sometimes multiple treatments are required at the recommended interval to get on top of an infestation by killing all the fleas as they emerge into adulthood.
2. Hormones which make the adult female fleas sterile: These are hormones that can enter your pet's blood stream and whilst they have no effect on the pet, when a female flea bites and drinks the blood, the hormone effectively sterilises her, so that any eggs she lays will not hatch. This can be a good way to prevent fleas from coming back but since adult fleas are not killed you may need to use another product in the meantime to remove them from your pet. These products also require the fleas to bite to be effective, and so are less suitable to those pets allergic to flea saliva.
3. Chemicals which prevent development of immature fleas: These can be applied to the environment and act as a growth regulator preventing the immature fleas developing into adults.

How can these treatments be given?

Topical treatment (on your pet's coat)

Treatments can be applied to the animal's coat in a number of ways and the available products vary in their effectiveness.

Some products are applied as a spot-on this means you put a small drop of the drug onto the skin at the back of your pet's neck (where they cannot reach to lick or rub it off). The active chemical in the product spreads through the pets coat and kills fleas on the skin. Sprays (aerosol or pump action) are also common methods of application.

Shampoos and powders are also available for flea control but generally only kill adult fleas on the pet at (or very soon after) the time of treatment. Since they do not persist for long in the coat they have to be reapplied often (sometimes weekly) which can be inconvenient. Shampoos are often used for young puppies and kittens as they are generally very safe.

Systemic treatments (given by mouth or injection)

These treatments are given to the pet, either as tablets or an injection, and enter its blood stream. When a flea bites and takes a drink of blood it also receives a dose of the product. These products act in a number of ways some reduce fertility in the adult fleas so that eggs laid do not hatch. Other products mimic hormones present in the young flea and stop the immature forms from developing to an adult.

Can I put a collar on my pet to control fleas?

Most flea collars sold in supermarkets and pet shops containing insecticides to control fleas are not very effective. They often only affect fleas very close to the collar and by the time a flea gets there it may already have bitten your pet elsewhere. There are newer flea collars that are effective, have safety catch mechanism to prevent them causing harm if they get caught and last for months - your vet will be able to discuss with you if this is a good option for your pet.  

The ultrasonic flea collars probably do not work. 

My pet won't keep still to let me spray them what do I do?

The chemicals used to kill fleas are produced in all sorts of formulations. You will usually be able to find a product to suit your needs. If you are really unable to treat your pet by yourself, you may need to get someone to help you hold your pet. This may be a friend or a professional (dog groomer, or veterinary nurse). 

Some products can be given my mouth (tablet for dogs or liquid placed on food for cats) or injection and you may find it easier to treat your pet in this way. 

How often do I need to treat my pet?

Fleas can breed and cause problems all year round in centrally heated homes. Regular treatment with the products recommended by your vet should keep fleas under control. The interval between treatments will depend on your particular circumstances and the products that you use. In most cases you will need to treat your pet's coat at least every 3 months (and with some products as often as once a week). Some products are given monthly by mouth. The key to success of whichever product you choose is to use it regularly according to the manufacturer's guide.

Why do I need to treat the house as well as my pet?

Only the adult forms of the flea live on your pet. The immature forms (larvae) are tiny maggot-like creatures that live in carpets, soft furnishings, and your pet's bedding. If you are going to tackle fleas you must address this pool of developing parasites that are ready to leap back onto your pet as soon as you remove the resident adult fleas. It is important to treat the areas where your pet spends most of its time - particularly the places where it sleeps. Washing your pet's bedding in hot water will destroy the young fleas (but not the eggs) and vacuuming your carpets also helps keep the numbers down. Vacuum bags should be disposed of to prevent collected immature flea stages continuing to develop in the house. Cleaning carpets with a steam cleaner should kill some of the larval fleas, and also remove the bits of organic matter that accumulate in carpets that the larvae feed on. Anything that is heavily infested, such as pet bedding, should be disposed of. However, in most cases you will need to use a chemical to kill the immature fleas as well as the adults.

What products can I use to remove fleas from the house?

Insecticide spray treatments can be used on carpets to reduce numbers of fleas. Some products target the adult flea whilst others are growth regulators that prevent eggs from hatching and the larval fleas from turning into adults that can re-infect your pet. Vacuuming the house first is a good tip: the warmth and vibrations mimic an animal walking by and stimulate the fleas to hatch, and these will then be killed by the spray treatment.

You must never apply a product designed for use in the environment directly to an animal. However there are some products that you can apply to your pet that will also have an effect on fleas living in the areas where your pet spends a lot of time.

Your vet can advise you on which product, or combination of products, to use. You must continue to treat your pet and your home all year round, even if you do not see fleas.

How do I stop fleas coming back?

Unless you remove all the immature fleas from your house they will keep getting back onto your pet. There are a number of ways of preventing your pet being re-infested with fleas.

Long-acting products can be used to kill all the flea stages in the house. In order to do this effectively the whole house must be treated which is expensive and difficult as immature fleas often live in hard-to-reach places. Many people find that they prefer to use something that prevent the immature forms from developing into adult fleas. If you can break the fleas' lifecycle so that adults are not produced they will not be able to reproduce. There are number of products that will do this but they must be given to all cats and dogs in the household. These products do not affect adult fleas. Alternatively a long-acting treatment that kills adults on the infested animal can be used on all animals in the household which will prevent egg laying and thereby break the cycle. Treating pets regularly should mean that the cycle is broken as new eggs will not be laid.

How safe are flea control products?

Most products are very safe if used strictly according to the manufacturer's instructions. Always follow these simple rules:

  • Read the instructions carefully before using the product.
  • Never treat a cat with a product designed for use in a dog (unless instructed by your vet). Cats are particularly susceptible to developing toxic reactions to flea control products containing traditional insecticides.
  • Never treat an animal directly with a product designed for use in the environment.
  • Do not apply the product more often than recommended by the manufacturer.
  • If treating a young anima,l ensure the product is safe for that age.
  • Do not combine products (unless instructed to do so by your vet).
  • Where possible treat animals in a well-ventilated area and after treating the house air well before accessing again.

Some animals can also be sensitive to other chemicals in the flea control product.