Common signs of a Flea infestation include:

.Live adults: Adult fleas are around 2-7mm in length, brown in colour and have narrow bodies to allow them to travel through pet hair easily. The main fleas in the UK are cat, dog and human fleas.
. Droppings: Fine black droppings found on animal skin or can easily be spotted against white backgrounds when droppings fall from animal fur
.Eggs and larvae: Female Fleas lay their eggs in nests, pet bedding, soft furnishing and cracks and crevices in a property. The eggs are around 0.5mm in size and white. After around a week, the eggs hatch into larvae that are around 1-4mm in length.
 .Pets scratching: The most common and known sign of a flea infestation is increased scratching from the pet host. 
.Bites: Flea bites normally look like small, red lumps on your skin and are normally found in scattered pattern on your lower legs – often around your ankles and feet. These lumps can be extremely itchy or painful, and you may be able to see a small hole or puncture mark (called a punctum) in the middle of the bite.