Treating Fleas & Other Parasites

Author: Danielle Fletcher
Published: Monday 23rd September 2013
Updated: Thursday 23rd January 2020

An introduction to fleas: general information, symptoms & conditions.

Fleas are ectoparasites, meaning that they live on the skin of their hosts, just like many other parasites of pets such as ticks and lice. With 63 species found in the UK alone, they are thought to be the most commonly caught parasites affecting our pets and even indoor animals may be at risk due to the sheer number of flea eggs present in the environment, which can be easily spread to your home. Two in particular, Ctenocephalides felis, and Ctenocephalides canis affect cats and dogs respectively.

Normally, the first signs of infestation will be:

  • your pet persistently scratching
  • small brown insects on its skin between the fur
  • brown-black flecks on its fur or bedding that looks like dirt. When transferred onto a damp tissue, if the "dirt" produces a red ring around the particles, it indicates that it is flea droppings, containing blood.

Fleas, like ticks and lice, feed on blood. When they bite, their saliva causes the broken skin to react, producing a swollen and red, itchy (pruritus) lump causing discomfort and irritation. In some cases, intermittent, repeated exposure to high numbers of fleas produces Flea Allergic Dermatitis (FAD). An animal suffering from FAD experiences intense reactions to flea bites, as over multiple infestations the animal becomes highly sensitised to the fleas' saliva. FAD symptoms include hair loss, superficial and severe skin infections (pyoderma), resulting in self-mutilation and a very unhappy pet! Parasitic Anaemia is another problem posed by heavy flea infestations, particularly in young animals such as puppies and kittens. Because fleas are blood-sucking, a smaller animal with a heavy burden may even lose fatal amounts of blood to the parasites, making the use of flea prevention and treatment products vital in young animals, or for use with pregnant or lactating females to prevent transmission to offspring.

While only the adults bite and cause distress, the majority of the population are not found on the animal itself. Around 95% of fleas, mainly larvae and pupae, live around our household, deep within carpets, bedding, sofas and in crevices between the skirting and floorboards. Female fleas can lay between 30 and 50 eggs per day, so just 50 female fleas could release 2,500 eggs onto your pet in just one day, which drop off around your home. Even the most effective product used on your pet cannot combat the masses hiding in an infested home, so it is important to thoroughly vacuum floors, skirting and sofas, and to ensure that all bedding and rugs are washed at 60°C. The heat from a vacuum or central heating system will however contribute to promoting the development of earlier stages into adults which will then jump onto your pet. Without cleaning followed by treating the house with special products, pets will continue to accumulate fleas, and it is extremely likely that you will also be bitten!

Transmission of disease

One group of worms may be transmitted to animals via fleas. Tapeworms use fleas as an intermediate host, and if your pet ingests an infected flea whilst grooming, it is likely that it will become infected with parasitic worms also. Dogs with fleas are commonly treated for worms simultaneously.

Recommended Treatments

Products for the prevention and treatment of fleas are diverse and some are broad-spectrum, treating infestations of other blood-sucking parasites such as ticks, and some also treat infections caused by specific Parasitic worms.

Spot On products

Spot On products are topically applied (to the skin), normally between the shoulder blades where it is unlikely that the pet being treated will lick it off while it is drying. The products dissolve in the natural oils produced by sebaceous glands found on the skin and are spread over the entire body's surface in the oils, allowing contact with all fleas and other ectoparasites present, killing them. Some products contain more than one active ingredient and they may act together in different ways to increase the efficacy of clearing infestations. The animal must not be shampooed or allowed to swim in the first 48 hours to ensure a product binds sufficiently to the skin and hair. Products naturally wear off over time as skin and hair is shed and groomed, and monthly applications are advised to prevent re-infestation.

  • Frontline Spot On has been a leading flea and tick product since its release in 1996. It is effective against fleas for up to 8 weeks in dogs and 5 weeks in cats, additionally targeting ticks for 4 weeks in dogs and 2 weeks in cats. It can be purchased in blister packs of 3 or 6 single-use pipettes containing a solution of 10% w/v active ingredient Fipronil; one pipette size for cats, and multiple volumes depending on the size and weight of dogs. Fleas and ticks die within 24 hours of contact with the product, and any new fleas which jump onto an animal will also be killed. New ticks are not prevented from biting however they will die and may then be easily removed with a tick remover if they do not drop off. Suitable for treating pregnant and lactating bitches and queens, puppies and kittens over 8 weeks old.
  • Effipro Flea Treatment is an extremely safe, effective and affordable product, available for treating both dogs and cats. Effipro is non-drip, making it a preferred product for many users. It contains the same active ingredient (Fipronil) as leading product Frontline Spot On and has the same action time frame. Effipro offers greater advantage to pet owners in terms of good value for money. It is also available to buy in single blister packs, so you can purchase the exact number you desire, rather than having to buy six if you only need four. It too has multiple sized pipettes for dogs. Although Fipronil has been approved for use in breeding, pregnant or lactating bitches and queens, it is advisable to check with your vet before using Effipro Flea Treatment. Suitable for puppies and kittens over 8 weeks old.

frontline Spot On and Effipro Flea Treatment contain Fipronil. Fipronil, is a broad-spectrum, non-systemic (does not affect multiple parts of the body) insecticide and ascaride, effective against both fleas and ticks. It binds to GABA receptors within the nervous system of fleas and ticks and inhibits the flow of ions in nerve cells, leading to death. In the first 24 hours after treatment, you may notice more fleas on your pet. This is because the active ingredient causes them to become disorientated and they travel up the hairs before dying and dropping off. Frontline Spot On and Effipro Flea Treatment are both very safe and can be bought without a prescription. Fipronil binds with much greater affinity to insect receptors, and is not absorbed through the skin so will not pass into the bloodstream affecting your pet internally and does not pose any threat to humans.

  • Advantix is a more potent treatment for more severe flea infestations in dogs only. Advantix is a prescription-only product used to target a wide range of biting insects, and is used especially on dogs which travel with their owners abroad to Southern European or Mediterranean countries. In these countries ticks, sandflies and mosquitos spread diseases such as Lyme's Disease, Leishmaniasis and Heartworm. Advantix contains two active ingredients, Imidacloprid and Permethrin, that target the nervous system of the pests. Imidacloprid is present in other anti-flea products available for cats, however Permethrin is highly toxic to cats but has low toxicity to dogs and humans.
  • Advocate for cats and dogs also provides relief and protection from fleas (prescription required), however its primary focus is on the elimination of parasitic worms. Heartworm, Lungworm and Roundworm pose significant health risks to pets. It contains two active ingredients, Imidacloprid and Moxidectin.
  • Frontline Spot On Combo is a prescription-only product, with an extra ingredient to Frontline Spot On. It contains Fipronil and (S)-Methoprene, a chemical that mimics an insect hormone and acts to inhibit the development of the larval insect's sexual organs. It effectively sterilises the females so that they cannot produce eggs. This prevents a further reservoir of eggs and larvae from building up in your house and the population dies out. It protects against fleas for up to 8 weeks in dogs and 5 weeks in cats, but (S)-Methoprene acts as a back up if you forget to administer the following dose on time, as its effects last longer than those of Imidacloprid.

Advantix and Advocate eliminate the existing and protect against new parasites for up to 4 weeks in dogs and cats. Where the pests are prevalent and cases of worms are higher in certain areas, it is advisable to treat once or twice a month for optimum protection and your vet will advise you appropriately. Your vet will advise you on their suitability for young animals and pregnant females.

Imidacloprid is a man-made chemical, similar to natural nicotine which is found on the leaves on many plants acting as an insecticide. It is not absorbed through the skin and targets external skin-dwelling parasites. Moxidectin is absorbed through the skin and travels in the bloodstream, using it as a transport system to access internal parasites (the worms).

Of course, there is a great range of alternative Spot On products available and the ones described above we would recommend. Effipro is an excellent non-prescription treatment for fleas and ticks to eliminate existing infestations and provide lasting protection while being affordable. Prescription treatments such as Advocate target a wider range of parasites and this is particularly helpful as biting insects and arachnids often transmit other diseases and parasites to our pets.

Tablets and suspensions

Anti-flea tablets and suspensions (fluid containing solid particles) are orally administered to pets and are absorbed into the blood stream in the gut. They have systemic effects, acting on fleas on the entire body by traveling in the bloodstream and are taken up when the fleas take blood-meals. It is often advised to give oral treatments on a full stomach or with food to aid absorption. Oral treatments often target fleas at a certain point in their life cycle, for example the adult stage. It is very important to treat your house with a suitable insecticide and clean as advised above, to kill the eggs and larvae that would otherwise jump onto your pet when fully developed as adults.

  • Capstar Flea Tablets are available for cats and dogs without prescription, in blister packs of 6 tablets. They begin to take effect as quickly as 15 minutes after ingestion and are 100% effective within 24 hours. Capstar Flea Tablets contain Nitenpyram, a neurotoxin that blocks messages sent in the fleas' nervous systems, causing death. These tablets only target the adult fleas living on your pet and effects are short term. They are safe to use once per day if fleas persist. Suitable for animals over 4 weeks old and weighing over 1kg.
  • Program Tablets for Dogs and Program Suspension for Cats break the life cycle of fleas by sterilising the females with the active ingredient, Lufenuron. Animals should be treated monthly during the 6 month flea season. Within 24 hours no viable eggs are produced by adult females and the adult population is left to die off. New fleas from the environment are sterilised and also prevented from sparking a new infestation in your home. Suitable for puppies and kittens on solid food, and pregnant females.
  • Program Plus are available on prescription for a variety of dog sizes, and treat both flea and worm infestations.

Natural products

Natural products for the treatment of fleas, ticks and mosquitos contain naturally occurring ingredients often found in plants, and are 100% free of insecticides. It is thought that some natural dietary supplements may also provide some degree of protection.

  • Biospotix Spray and Biospotix Flea Spot On contain Geraniol, a main constituent many essential oils, including citronella oil, renowned for use in plant-based insect repellents. The products produce protective vapours around pets which act as barriers to deter biting insects. The Biospotix Flea Spot On provides 4 weeks of protection and comes in packs of 5 single-use pipettes, Biospotix Spray 500ml may be used weekly. Can be used on puppies and kittens over 3 months old.
  • Groomers Garlic Oil Food Additive and adding Garlic into your pets feed is thought to help deter fleas and Garlic may also help to promote general well-being.
  • Denes Liquid Garlic Spray contains ingredients Garlic and Aniseed to repel fleas and simultaneously aid healing of small cuts and bites when sprayed onto, or combed through pets' coats.

Sprays (for pets and the home)

The speed at which you will clear your flea infestation depends upon treating both your animals and your home. With such a good range of effective treatments like Spot Ons, many sprays aim to eliminate the large flea numbers (mainly eggs are larvae) which build up around your house, in bedding, carpets and between floorboards. Sprays are also commonly used to control dust mites, a common cause of human allergies and skin conditions in dogs.

To treat your home, you must first vacuum thoroughly and wash bedding at a high temperature (at least 60°C). Each product instructions are slightly different, however the normal mode of action is to remove all pets from the rooms to be treated and ensure that all floors, carpets, cracks, skirtings and soft furnishings are sprayed. Sprays have long-lasting effects and regular vacuuming will stimulate some fleas to hatch so that the adults are rapidly killed by the active ingredients, and other active ingredients will prevent development of eggs and larvae for up to a year, preventing infestation. Treating pets with suitable products at the same time will protect them and your home most effectively. Here, we recommend some award-winning household sprays:

  • Indorex Household Flea Spray has been voted Best Product for two years running by the readers of ‘Your Dog’ magazine! It provides safe, effective protection, active against adult fleas for 2 months, and preventing development of immature stages, ticks and dust mites for 12 months. It has added advantages- it is odourless, colourless and is unlikely to stain upholstery. It is the only product stable in UV light, so will not lose its effectiveness when exposed to sunlight. It has the highest Permethrin content of any spray, and uses an additional ingredient (Piperonyl Butoxide) to enhance the rapid killing action and long term staying power of Permethrin. Piriproxyfen prevents flea and dust mite eggs from hatching for 12 months.
  • Genitrix RIP Fleas Household Spray is a triple action, long-lasting insecticidal spray. The first active ingredient, Bioallethrin, causes paralysis of adult fleas but is extremely safe for household use. It allows the second active ingredient, Permethrin, more time to come into contact with and kill adult fleas. The third, (S)-Methoprene, inhibits development of immature stages so that fewer adults hatch (those which do are killed). Genitrix RIP Fleas Household Spray is effective for up to 12 months and also kills ticks and dust mites.
  • Acclaim Household Fleas Treatment also contains Permethrin and (S)-Methoprene to kill adults and prevent immature stages from hatching. It is effective against fleas, ticks, ants and silverfish among many other unwanted crawling pests found around your home!

Permethrin : this man-made chemical imitates the action of a natural insecticide. It is lethal to insects as it binds strongly to the receptors in their nervous system, leading to death of fleas and other pests. It is harmless to many mammals including dogs and humans because it does not react with most mammalian receptors. As mentioned in the Spot On section, it does have a marked effect on cats when ingested or applied to the skin. For this reason, it is never present in products for use directly on cats, but it is safe to use in a cat's environment. When treating a room, pets must always be removed from the room until the product had dried onto the household surfaces. It does not pose a risk to feline health when used in household sprays.

  • Bob Martin Flea Bomb is a safe, quick method to treat the rooms of your house. It begins to take effect after just 15 minutes and helps in the long-term management of infestations.

If you prefer, you could call in a pest control team to treat your home for you, but this may be costly and the products themselves are very easy to use.


Shampoos provide short term relief of flea, lice and tick infestations. They are normally required weekly and are slightly more inconvenient to use than other products. On the other hand, they help to keep your pets clean and their coats glossy so the extra effort may be worth it! As with previously described products, some are suitable for dogs or cats only, and others contain biodegradable natural insect repellents preferred by some pet owners.

  • Beaphar Flea Shampoo is for dogs only (it contains Permethrin). It is effective for a maximum of 7 days and is suitable for use on puppies aged over 12 weeks.
  • Johnsons Cat Flea Cleanser and Johnsons Dog Flea Cleanser are shampoos formulated for cats and dogs with natural, citrus-based ingredients to repel fleas. Natural herbal extracts help to condition the coat, making them suitable for regular use.
  • Johnsons Dog Flea Shampoo (Insecticidal) contains a natural insecticide, Pyrethrum extracted from the Chrysanthemum flower to kill fleas (Permethrin is a synthetic derivative used in many other products and is only suitable for dogs). Again, effects are short term but it is suitable for weekly use, and for use on puppies over 12 weeks old.

Of course, it is important to find the products to best suit both you and your pet. The take home message is that both your pets and home must be treated to eliminate pest infestations, with regular treatments best way to protect against future pests from taking hold.

If a pet is diagnosed with FAD by your vet, many of these products are great at providing fast relief of symptoms and infestations, allowing for an improved recovery.

We hope that this article has been helpful in outlining the products and methods available. If you feel that you would like more information, do not hesitate to contact us!