An in-depth guide to fleas on dogs


Should your dog have fleas, they can multiply rapidly and since they aren't averse to snacking on humans, they can make both your lives a misery.

Life cycle of fleas

Adult fleas mate while on your pet, and the resulting eggs that are laid fall off as he wanders around - so everywhere he goes, and particularly in those places where he spends a lot of time (such as his bed), he may be shedding hundreds, or even thousands, of eggs. These eggs can also be carried on your shoes and clothing into other people's homes.

After one or two days the eggs hatch into larvae, which wriggle away from the light and feed on environmental debris such as adult flea droppings and human skin scales. After three moulting stages the mature larvae then spin themselves cocoons, which protect them as they develop into adult fleas. They can survive in this state for up to two years if conditions are unfavourable, but when alerted by heat, motion, vibration or an increase in carbon dioxide levels to the presence of a possible host, they hatch out and jump on to the first available source of food.

They feed by inserting their long mouthparts into the skin, followed by an injection of saliva to prevent the blood they suck from their host from clotting, and it's this saliva that causes irritation, rather than the bite.

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Diseases caused by fleas

Flea bites can trigger allergic skin reactions in some dogs, leading to inflamed itchy areas which can develop into large open sores and hair loss, causing intense misery to the afflicted animal. Fleas can also infect your pet with tapeworm, and can be responsible for the transmission of two bacteria known to cause mild flu-like symptoms, fever and a skin rash in humans.

Finding fleas on dogs

An obvious sign of fleas being around is that you notice your pet scratching, biting, licking, chewing or rubbing more than usual; when parting his coat you may also see tell-tale pink bite marks on his skin. But just because you don't see any fleas, it doesn't mean there aren't any around - check for flea droppings in your dog's coat. They'll look like dark specks; flick them off with a brush on to a piece of damp white paper, and if they are indeed flea dirt, rather than bits of dried mud, they'll dissolve, leaving reddish brown stains.

Flea treatments for dogs

There are many anti-flea products available, including those that are insecticidal, some which repel and others that act as a kind of flea contraceptive. The latter can be helpful in preventing resistance developing to regularly used products, as the relevant genes for resistance can't be passed on.

Some products also have different methods of administration - collars, powders, shampoos, sprays, tablets and ‘spot-on' treatments - and depending on the individual product, the length of time they remain effective can vary from 24 hours to three months. Some products act faster than others, killing fleas within three or four hours of administration, while others may take between 12 and 42 hours to begin killing fleas.

Furthermore, some treatments are multi-action and are effective against other nasties such as worms and ticks as well. With so much choice, it can be difficult to know what type of product to buy. Generally, the most effective are those available as prescription-only medications, so your vet is a good starting place to ask for advice about what is most suitable for your dog.

Rachael Greenland from Welshpool, Powys, prefers not to use chemicals if she can avoid it, and uses ‘alternative' methods of flea control for her dog instead...

"I did use spot-on treatments and environmental sprays to treat the house with our previous dog, but I'm not convinced they were in his best interests or even entirely necessary. Having looked into the subject in more detail since then, I feel that it's a case of using a sledgehammer to crack a walnut - I think there are other ways of dealing with the problem which are just as effective and don't run the risk of overloading my dog's system with chemicals.

"I've found neem to be very successful. Although we have found the occasional flea, they've been incredibly sluggish, so it's been easy to catch and dispose of them, and we certainly haven't had any major outbreaks.

"Neem is a natural, non-toxic oil from the tropical neem tree, and has been reported as being effective in controlling over 600 types of pest, so I think we're pretty well covered on all fronts now!"

Did you know?

  • Under optimum conditions, the time from a flea egg being laid to becoming an adult can be as short as 15 days.
  • The most common species of flea found on dogs is the cat flea.
  • Some veterinary practices offer free ‘flea clinics' - your pet can be checked for fleas and you are offered advice on treatments available.
  • Fleas can jump up to 1m vertically.