It is recommended that you remove fleas before they increase in number. The adult flea is reddish brown in colour with the most distinctive feature being the large jumping legs. Their mouthparts of the flea are adapted so they can suck blood. Fleas can reach a height of 7 inches when jumping. Their bodies are laterally compressed, permitting easy movement through the hairs or feathers on the host’s body (or in the case of humans, under clothing).
Fleas can live for one or more years depending on the conditions. Newly emerged fleas without a host for food will only live for a few days
Though dogs, cats and foxes are the ideal hosts for fleas they are capable of feeding on humans. Bites cause an itching sensation which in turn may result in the host attempting to remove the pest by biting, pecking, scratching, etc. in the vicinity of the parasite. Flea bites generally cause the formation of a slightly raised, swollen itching spot with a single puncture point at the centre (similar to a mosquito bite).
Remove Fleas - Effective Pest Control from Merlin Services Wiltshire
The bites often appear in clusters or lines of two bites, and can remain itchy and inflamed for up to several weeks afterwards. Fleas can also lead to hair loss as a result of frequent scratching and biting by the animal, and can cause anaemia in extreme cases. They can also act as a vector for disease to remove fleas as soon as possible.
More details about the flea are at this Wikipedia link.