Flea bites can cause dermatosis such as urticaria.
Flea adults lay eggs on animals and fall into nests, and larvae are hatched. Larvae grow in nests or moist places, and spin silk to make cocoons when they mature. In the cocoons the larvae develop into pupae. When the pupae mature, they break out the cocoons and develop into adults. Female fleas can lay eggs within 1 - 4 days after sucking blood. The development from eggs to adults needs about 3 weeks.
Figure 1 flea
Adult fleas are about 1 - 4mm in size, wingless, brown. Although the flea body is short, the feet are long and well developed. Fleas are good at jumping, and can jump 19.5cm high and 33cm long. Their mouthparts are thin and long, in favor of piercing the skin and sucking blood. The fleas often parasitize human skin or animal hairs, or hide in damp places such as wall corners, floor cracks, and bed boards.
Signs and Symptoms
Fleas bite the skin of humans and animals with their sharp mouthparts, and the blood sucked is their only source of food. Both male and female fleas suck blood. Adult fleas suck blood several times daily. Each sucking blood lasts for 2 - 3 minutes, and the venom discharged by the mouthparts are injected into the skin while sucking blood, which can cause inflammation of the skin.
Figure 2 flea bites
Some individuals have no reactions after bites, and some may develop erythema, papules, or wheals. Local skin redness and swelling and severe pruritus may be present. There may be pinpoint sized purplish red spots on the the center of the lesions, which are the marks of bites. Vesicles may occur on the red and swollen skin. The skin lesions are often linear or in groups, mostly on the waist, abdomen, and calves, prominently in children. There may be papular urticaria, with severe pruritus. Scratch marks, blood scabs, and secondary infections are often seen on account of scratches.
If sudden pruritus occurs on the waist or calves, and there are scattered edematous erythema and wheals, flea bites should be considered. If fleas are found on the human body, the disease can be definitively diagnosed.
Topical calamine lotion is appropriate. If there are severe reactions, antihistamines can be administered.
Fleas can be eliminated with insecticides such as dinotefuran.