The science behind the scratching: understanding flea treatments for dogs

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Fleas can do a lot more than simply make your dog itch so it’s essential to treat infestations with an effective flea treatment and to keep this up regularly to help keep your dog protected.

Fleas are one of the most common parasites affecting pets and they can appear when you least expect them. It’s important to understand a bit about the flea’s life cycle and how flea treatments for dogs actually work, before following a few simple steps to help keep your pets protected.

Understanding the flea life cycle

Fleas are tiny wingless insects that feed on your dog’s blood. Female fleas living on your dog lay eggs, which fall into the surrounding environment (e.g. your home!) where they hatch into flea larvae. The larvae turn into pupae and then into adult fleas. Each juvenile flea waits inside a tiny cocoon until a new host animal comes along. When they sense body heat and vibrations, the young fleas burst from the cocoon, leap onto the nearest pet (or person!) and start to bite. On pets, breeding begins, more eggs are produced, and the whole horrible cycle starts again.

Fleas can mean worms, too

Flea bites are painful and itchy, and the sight of your dog constantly scratching or licking at his irritated skin is often the first sign of an infestation. You won’t always know if your dog has fleas though, because they burrow deep into the hair coat and can’t always be seen.

As well as irritating your dog’s skin, fleas pose other health dangers too. Fleas can be infected with tapeworm eggs, and if fleas are swallowed (which is common when pets groom themselves), this can lead to a tapeworm living inside your dog. The loss of blood from multiple flea bites can also be particularly dangerous for puppies, and small breeds, elderly dogs or pregnant dogs may also be at a higher risk from a heavy infestation. If you are concerned that your pet has a very high number of fleas or seems unwell then it’s always worth getting some advice from your vet.

Treating and beating fleas

If you think your pet has fleas, you need to act fast. There are a range of treatments available for fleas including spot-ons, collars, tablets and sprays. The active ingredient in the spot-on Advantage spreads rapidly throughout the skin of your pet, and is able to kill fleas on contact, meaning that fleas do not have to bite your pet to be killed.1 Make sure you buy an appropriate product for your dog’s age and weight.

After you’ve treated your dog, you need to move on to your home. Fleas can lay eggs everywhere, and it’s important to vacuum your home and car, wash your pet’s bedding, and clean upholstery. Use a veterinary approved household flea spray to help kill flea life stages in your home, it’s important to do this thoroughly, including under sofas and beds etc. as fleas can get everywhere!

How treatments work

In addition to killing adult fleas, flea treatments usually interrupt the flea life cycle by killing fleas on your pet before they have a chance to lay eggs around your home. Some products also have a direct effect on the immature flea stages. Imidacloprid in Advantage for example is able to kill flea larvae in addition to adult fleas. Monthly spot-on drops like Advantage can be purchased from many local pet stores.

Did you know…

The popularity of flea circuses is mainly down to an Italian, Louis Bertolotto, whose flea circus was all the rage in London in the 1830s and carried on for over half a century. His fleas even performed in front of heads of state all around Europe.

Find out more about Advantage spot-on treatment here.


1 This information is regarding mode of action and is not intended to imply fleas can be completely stopped from biting; Mehlhorn et al. Parasitol Res (2001) 87: 198-208

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L.GB.MKT.07.2018.19023

July 2021

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