Fleas are the archetypal blood-sucking parasites. There are 2,200 species but only a few that commonly infest dogs and cats, the most common being the cat flea, or Ctenocephalides felis. Its dark brown or black body measures 1-3 millimetres long and it can jump up to 60cm high,10,000 times in a row. You’ll usually find fleas on a dog’s abdomen, the base of the tail and the head, although a heavy infestation can thrive anywhere on the body. However, even if you can't see any fleas, it doesn't necessarily mean your dog doesn't have them. The most obvious signs are excessive scratching, licking or biting at body parts, which may in turn cause rashes, scaly skin, hot spots and hair loss. You may even see droppings, or flea dirt, in your dog’s coat.