Fleas 101

Health risks crash course

“I’ve never seen a flea, so my pet doesn’t have fleas.” As vets we’ve heard this many times and wish it was true. Unfortunately, just because you can’t see fleas, doesn’t mean your pet is flea-free. 

Not only do fleas cause a huge amount of discomfort for your pets…there are other health-factors to take into consideration. That’s why consistent flea prevention is so important. This blog will cover all the main health risks that fleas pose for your pets, and also to you and your family. 

First let’s cover the big one and the major reason why many owners end up at the vets. Live fleas are ITCHY! Flea bites are uncomfortable and cause itchiness in our furry family members and potentially, the rest of the family. Fleas aren’t picky about where their meal comes from (blood) and will bite any warm body near them, meaning you and your family are fair game for these parasites. Animals will obsessively lick, bite, chew and can even become extremely stressed when infested with fleas. Not to mention they’ll be keeping you up at night doing so. 

Now that we’ve covered the most common reason owners reach for flea prevention, it’s even more important we cover the health issues that can create an even bigger problem.

Flea Allergy Dermatitis

A step above your average itchy flea bite is referred to as flea allergy dermatitis (FAD). Some pets have an immune hypersensitivity or allergy to flea saliva, and when bitten a more severe local reaction will occur. Affected animals will lick and chew themselves in response to a bite to the point of hair loss, severe redness and even secondary bacterial or yeast infections. These pets absolutely should be treated regularly for fleas to decrease the chances of experiencing these types of outbreaks, as they are often painful. Pets that suffer from FAD often need to seek veterinary care for topical and/or oral medications like antibiotics, anti-inflammatories, sprays, and shampoos to help treat the skin. 

Environmental flea infestation

Just because you can’t see fleas doesn’t mean they aren’t there. Live adult fleas are small and quick! Adults can be seen with the naked eye, are dark brown in colour and only a few millimetres in length. They like to jump around but also burrow deep within the fur to plan their next “blood meal” (bite). Eggs however, can’t be seen so easily and are produced in large quantities which can remain on your pet, or are shed into the environment. These eggs mature into larvae which are both persistent and resistant. They love to hide in carpet, bedding, furniture, etc. Adults will emerge weeks down the road and begin the life cycle again. As vets we often find live fleas or flea poo on many pets when owners insist their pet doesn’t have fleas. Fleas prefer moderate weather, however it takes several days of sub-freezing temperatures for the flea life cycle to be interrupted. This means that in a moderate climate like the UK, year round prevention is necessary. It’s also common for vets to recommend prevention year round regardless of weather because of other parasites that are also prevented by flea treatments, such as ticks. 

Due to their short life cycle, affinity for moderate temperatures and ability to persist in the environment – regular flea prevention is all the more important. 

Flea borne diseases

If you aren’t disgusted enough already, unfortunately there’s more. Fleas can carry other diseases that can cause your pet (or you) to become ill. Historically, fleas have been the culprit to harbouring and spreading the bacterias guilty of causing plague and typhus in humans. Additionally, fleas are also the transmitter of the bacteria Bartonella, better known as cat scratch fever. Bartonella may cause infected cats to become unwell and can be spread to humans by a cat scratch. Mycoplasma haemophilus is another bacteria spread through fleas, and is a major concern for cats that spend time outdoors. This nasty bacteria can cause cats’ red blood cells to be recognised as foreign and destroyed, leading to potentially life threatening anaemia. Fleas also commonly carry the egg of the tapeworm Dipylidium, which if swallowed by your pet or humans will lead to development of the tapeworm along the intestinal tract.


When it comes down to it, not only are fleas annoying, they also pose a health risk to you and your pets. For this reason, vets encourage pet owners to be proactive in preventing fleas year round. There are many products on the market which can be overwhelming for owners. Which is right for your pet? Why are there so many? Why do I need a prescription when I can buy some over the counter? In general, preventative treatments containing medication are going to be the most effective. Unfortunately “all natural products” will not achieve the results we desire in most cases. 

VetBox subscriptions are tailored to your pet by our team of qualified vets and the treatments are sent automatically in the post each month. Fill out our quick online sign-up form to find the best treatment for your dog or cat. For pets with specific requirements, our vets can tailor their subscription even further so please get in touch to discuss. 

Dr. Kirsten Ronngren, DVM – MRCVS

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