Fleas and ticks are the most common external parasites (ectoparasites) that affect cats and dogs in the UK.

Fleas

Fleas cause discomfort to the animal, can result in allergic dermatitis and can also transmit tapeworm infection.

Signs of flea infestation might not be obvious in a nonallergic animal. Cats and dogs most often become infested with newly-emerged fleas from the environment, but they can also pick up fleas from close contact with other infested animals. Combing the pet's fur is the best way of detecting fleas and, if an animal has an infestation, an insecticide can be used to kill the fleas. Treatment may need to be repeated until the problem is controlled. It is also important to treat other pets living in the same house.

Adult fleas on the animal are only part of the problem, so it is also crucial to eliminate fleas that are in their immature stages from the home. Regular use of insecticides on the animal will contribute to the reduction of immature fleas, but environmental measures are also needed, including vacuuming carpets, washing the animal's bedding and using products designed to kill fleas that are in their developmental stages.

A lack of understanding of the need to attend to the environment may underlie pet owners' frustration about the apparent lack of effect of flea treatments used on pets. Monthly flea prophylaxis (treatment) is recommended for most cats and dogs.