Fleas are wingless insects with mouthparts adapted for piercing skin and sucking blood. Fleas are external parasites, living by hematophagy or off the blood of mammals. Fleas are small, agile, and usually dark colored. They are found indoors in floor cracks and crevices, along baseboards, under rug edges and in furniture or beds. Fleas are not only a nuisance to humans and their pets, but can cause medical problems including flea allergy dermatitis (FAD), secondary skin irritations and, in extreme cases, anemia, tapeworms, and stomach flu.